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Visual quality improvement in refractive surgery

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Visual Quality Improvement inRefractive Surgery

Visual Quality Improvement in Refractive Surgery

Ruth Lapid-Gortzak

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Promotieboek_omslag_DEF.indd 1 26-09-10 00:04

Visual Quality Improvement in Refractive Surgery

Promotieboek_omslag_DEF.indd 2 26-09-10 00:04

Visual Quality improVement in refractiVe surgery

Ruth Gortzak

ISBN: 978-94-90371-48-7

Publication of this thesis was financially supported by: Retina Total Eye Care, Alcon, Ophtec, Occulenti, Simovision, Dorc, Zeiss, Medical Workshop, Novartis, Thea pharma, Bausch and Lomb, Zonnestraal Ziekenhuizen, AMO Abbott.

Cover design: Dion Kikkert, DesignCrew.nl

Layout & printing: Off Page, offpage.nl

Copyright © 2010 by R. Lapid-Gortzak. All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means, without prior permission of the author.

Visual Quality improVement in refractiVe surgery

academisch proefschrift

ter verkrijging van de graad van doctoraan de Universiteit van Amsterdamop gezag van de Rector Magnificus

prof. dr. D.C. van den Boomten overstaan van een door het

college voor promoties ingestelde commissie,in het openbaar te verdedigen in de Agnietenkapel

op donderdag 16 december 2010, te 14:00 uur

door

ruth gortzakGeboren te Amsterdam

promotiecommissie

Promotor: Prof. Dr. M.P. Mourits

Co-promotor: Dr. T.J.T.P. van den Berg

Overige leden: Prof. Dr. C.M.A.M. van der Horst Prof. Dr. A.G.J.M. van Leeuwen Prof. Dr. M.M. Levi Dr. T. Lifshitz Prof. drs. C.C. Sterk Dr. F.D. Verbraak Dr. M.A. Landesz

faculteit der geneeskunde

General Introduction 9

Advanced Personalized Nomogram for Myopic Laser Surgery: First 100 eyes 53

LASIK and LASEK after Refractive Lens Exchange with Diffractive Multifocal IOL Implantation 63

Straylight Measurements in Laser In Situ Keratomileusis and Laser-assisted Subepithelial Keratectomy for Myopia 75

Straylight Before and After Hyperopic LASIK and LASEK 87

Straylight Measurements Before and After Removal of Epithelial Ingrowth 101

Herpes Simplex Virus Keratitis After Laser in Situ Keratomileusis 111

General Discussion 119

Summary 127Samenvatting 133Curriculum Vitae 140Words of Thanks 144

contents

chapter 1

chapter 2

chapter 3

chapter 4

chapter 5

chapter 6

chapter 7

chapter 8

addendum

In the loving memory of my mother

Nitza Gortzak-Moorstein

Ophthalmologist and teacher

May her memory be a blessing

לזכרה של אמינצה גורצק-מורשטיין ז”ל,

מורתי, רופאת עיניים.

GeNeRAL INTRODUCTION

1 1.1 Why do patients seek refractiVe surgery?

Refractive surgery is the procedure by which a refractive error, such as myopia, hyperopia, or astigmatism is treated. The procedure utilizes a variety of technical possibilities to achieve the goal of emmetropia. Patients who seek a refractive procedure are motivated to undergo an elective procedure that will enhance their vision without the need for optical correction.1 The procedure should be as short, safe, and as accurate as possible. The side effects are well known2; surfing the web a large number of sites will be found which contain information about the complications and potential dangers of refractive surgery. Still, in the majority of cases the outcomes are acceptable to excellent1, and most patients gain the spectacle freedom they were seeking, with high satisfaction in terms of improved uncorrected vision, recreation, and comfort.3-4

Does patient satisfaction correlate with visual quality? This depends on the definition used. Patient satisfaction with visual quality basically depends on patient expectations, and patient experience with vision. Patients may have such a gradual deterioration of visual acuity, that for example they may have a Snellen vision that is not sufficient to drive a car, but may not have yet noticed this. The other extreme are people with severe complaints despite the fact that there is no corroboration on objective testing such as recurrent testing of Snellen acuity, wavefront measurement, contrast sensitivity, and straylight. Subjective visual quality is determined by a plethora of physical phenomena as well as psychological phenomena.5

1.2 introduction to refractiVe surgery

1.2.1 history of refractive surgeryRefractive surgery has been around since Schiotz noted that one could change the form of the cornea with incisional surgery in 1885.6 Lans demonstrated that incisional or thermal surgery could reshape the cornea, and with it the refraction, but had poor long-term outcomes. Nowadays refractive surgery is a combination of different techniques that enable us to change refractive errors in the eye.6-7

Techniques commonly utilized are corneal laser surgery, implant lenses, conductive keratoplasty techniques (in which the cornea is heated in a ‘controlled’ manner, which induces a surface change), or any combination of the current techniques.

1.2.2 aims of refractive surgeryThe aim is to achieve a certain refractive goal. This may be a refraction of plano (0 Diopters (D)) to have a good unaided distance vision. This may also be a refractive error that is on purpose left undercorrected between -1.5 D and -2.00 D to have a reading acuity in a presbyopic eye (age related farsightedness, in which accommodation is not sufficient for near vision any longer). The aim may also be certain multifocality, such as with multifocal implant lenses, but also other modalities that achieve monovision try to attain this, such as intra-corneal inlays, or intrastromal femtosecond treatments like

10


1Intracor, in which the corneal shape is changed with different modalities in order to achieve multifocality of some sort.8

1.2.3 technologies in refractive surgeryThe surgical modalities in use are the excimer laser, the femtosecond laser, conductive keratoplasty, scleral imbrication, various types of keratotomy procedures, be it T-cuts or radial cuts or opposing clear cornea incisions, placement of intra-ocular lenses in the anterior chamber, or in the posterior chamber, and refractive lens exchange. Slowly but surely cataract surgery is moving in the direction of refractive surgery, because of the possibility of achieving accurate refractive results and achieving a high rate of spectacle independence for the patients. The quality of cataract surgery is improved by implementing the successes of refractive surgery; this creates a win-win situation.

The techniques used in this thesis are: Laser assisted sub-epithelial keratomileusis (LASeK), Laser in-situ keratomileusis (LASIK), Photorefractive Keratectomy (PRK), cataract surgery, refractive lens exchange (RLe), and bioptics.

In corneal laser surgery laser energy is used to ablate corneal tissue to change the curvature of the cornea. In myopia we want to flatten the corneal curvature, by centrally ablating tissue. In hyperopia the cornea is steepened by peripheral removal of tissue with the laser ablation. The ablation pattern (diameter and depth) are determined by the laser nomogram used.

In LASeK and PRK the corneal epithelium is removed and the laser beam is applied to the Bowmans membrane, which is ablated, together with the stromal tissue underneath it. The ablated area is then rinsed with balanced salt solution. In PRK a bandage contact lens is applied directly over the ablated cornea. In LASeK the preserved and removed epithelium is repositioned over the ablated cornea, and then a bandage contact lens is applied.

In LASIK a hinged flap is cut into the cornea. The diameter and the depth of the flap are determined by the instruments used. Microkeratomes are mechanical devices that cut the flap and have set depths of cutting. Femtosecond lasers allow for tailor made forms of the flap. The flap is lifted away from the stroma, and the laser ablation is applied directly to the deeper stroma. After the ablation the corneal flap is replaced and properly appositioned. In this method the incisional surface is very small, and patient comfort is rapidly improved, vision is restored within a very short time period.

In cataract surgery and RLe the crystalline lens is removed and an intraocular lens (IOL) is implanted in its stead. These implants can be of different materials, and may have one or more foci. The dioptric strength of the implant is determined after biometry of the eye. In cataract surgery and RLe it is possible to achieve a plano refractive outcome, that is, reduce the patients’ dependence on visual aids.

Bioptics is the situation in which there is a residual refractive error, which is disturbing to the patient, and can be corrected with corneal laser surgery.

There are other techniques, like intracorneal stromal rings and phakic IOLs, that all address a refractive error. These techniques are beyond the scope of this thesis.

11


1 1.2.4 reasons for having a refractive procedureThe top five reasons to have refractive surgery were described by Khan-Lim et al.9 The main reason for having refractive surgery was the freedom from glasses or contact lenses. Think of walking in the rain with your glasses, or changing your contact lenses in the windy desert. The subsequent reason was contact lens intolerance, often seen after years of intensive wear of soft contact lenses. Discomfort caused by glasses or contact lenses was another reason; this can be caused by the weight of the glasses on the nose and ears, or by the manipulation of the eyes in order to wear contact lenses. Cosmetic reasons are in the fourth place. Interestingly in my practice this is a rarely mentioned cause. The fifth reason is sporting activities, like in contact sports. This is also true for professional activities which might be better and more safely performed without optical correction, like in the commercial (naval) professions, military, fire brigade, or the police.

1.2.5 tailor-made treatmentDifferent treatment modalities can treat different refractive errors. The treatment should be tailored to the wishes of the patient on the one hand, and the physical properties of the patient and the eye on the other hand. The expectations of the patient should match the technological possibilities. This needs to be determined pre-operatively. each treatment has its own safety profile, and this needs to be discussed with the patient pre-operatively in order for the patient to give consent.

The following paragraphs will describe the technologies and science that are relevant to the studies. The common denominator is that, wavefront technology, visual acuity testing, contrast sensitivity, straylight, and patient satisfaction, together lead to the outcomes in refractive surgery.

figure 1: Time line of development of corneal refractive surgery techniques.

9

operatively. Each treatment has its own safety profile, and this needs to be discussed

with the patient pre-operatively in order for the patient to give consent.

Figure1: Time line of development of corneal refractive surgery techniques.

The following paragraphs will describe the technologies and science that are relevant to

the studies. The common denominator is that, wavefront technology, visual acuity

testing, contrast sensitivity, straylight, and patient satisfaction, together lead to the

outcomes in refractive surgery.

12


1table 1: Treatment modalities in refractive surgery

treatment modalityrefractive error treated preferred age group technology

LASIK Myopia, hyperopia, astigmatism, some presbyopia

Accommodating patients, or monovision in the presbyopic patient

excimer laserFemtosecond laser

LASeK Myopia, hyperopia, astigmatism, some presbyopia

Accommodating patients, or monovision in the presbyopic patient

excimer laser

Keratotomy Astigmatism on steep axis

Any age Incisional

Conductive keratoplasty

Mild hyperopia and presbyopia

Presbyopes Radiowaves

Intracor Presbyopia Presbyopes and hyperopes up to +1.25 D

Femtosecond intracorneal

Intracorneal inlays Presbyopie Presbyopes and hyperopes up to +1.25 D

Intracorneal incision and implant

Phakic IOL*), angle supported

Myopia Accommodating myopes Intraocular lens (Acrysof Cachet type)

Phakic IOL*), iris enclavated

Myopia, astigmatism, hyperopia

Accommodating patients Intraocular lens (Artisane Verisyse type)

Phakic posterior chamber IOL*)

Myopia, hyperopia, astigmatism

Accommodating patients Intraocular lens (ICL type)

Cataract surgery Any refraction Patients with visual loss from cataract

Intraocular lenses

Refractive lens exchange (RLe)

Hyperopes, myopes with an axial length under 25 mm

Patients > 40 years old, motivated by their wish of freedom from optical correction

Intraocular lenses (monofocal, multifocal, refractive, diffractive, toric, combined toric with refractive, bifocal)

Bioptics Residual refractive error after lens implantation for cataract or RLe

Any age excimer laserFemtosecond laserLens or inlay implantation

*) IOL = intra-ocular lens

1.3 WaVefront technology, WaVefront guided treatments, and higher order aberrations

1.3.1 Wavefront technology and higher order aberrationsLight can be described in several ways. In classical geometrical optics, light rays that come from infinity are considered to be linear bundles of light, and the refraction is measured in spheres and cylinders. In physical optics light is considered a wave, and lights spreads in a spherical way in all directions. A wavefront of light comes into the eye, and every plane the wave encounters can change the direction and speed

13


1 of the wave and thus the shape of the wavefront. As such, light that was in phase within the wavefront can become out of phase, or aberrated. This can be measured by aberrometers. (See figure 2)

Spectacles can correct up to the second order aberrations, that is spheres and cylinders, all the higher order aberrations represent irregular astigmatism. Historically, irregular astigmatism used to be a refractive error that could not really be measured,

figure 2: A wavefront aberration is the deviation of the wavefront measured in an optical system when compared to the reference wavefront of an ideal optical system. In the Hartman Shack aberrometer a wave of light is projected with a laser and recorded through an array of lenslets, and the light returning from the optical system being measured is compared to the perfect optical system. The differences are measured and mapped out: the difference between the ‘perfect eye’ and the actual measurement are the higher order aberrations.

12

Figure 2: A wavefront aberration is the deviation of the wavefront measured in an

optical system when compared to the reference wavefront of an ideal optical system. In

the Hartman Shack aberrometer a wave of light is projected with a laser through an

14


1and was treated empirically with rigid gas permeable (RPG) contact lenses. We now know that irregular astigmatism is caused by higher order aberrations (HOA). Smirnov was the first to measure HOAs with a psychophysical method in 1961.10 In 1994 the first optical measurement of aberrations of the human eye were done using a Hartmann-Shack sensor.11 Using adaptive optics the correction of the HOA led to better optical quality in normal eyes.12 Mrochen et al were the first to publish the use of wavefront technology in refractive surgery.13 It was shown that even normal eyes with good uncorrected visual acuity had some form of irregular astigmatism, these are the HOA. These HOA depend on factors like blinking, tearfilm stability, ageing, and accommodative state.

Aberrometry today plays a role in refractive surgery, in getting ‘supervision’, but also diagnostic in forms of irregular astigmatism, and in the design of implant lenses and contact lenses. The HOA can be expressed as the total root mean square error (RMS), a set of coefficients from Zernike terms (Figure 3), Strehl ratio, point spread function, modulation transfer functions, and more coefficients. The HOA representation as RMS is numeric, and can be specific to a certain aberration, like coma or spherical aberration, or it can be in the form of a color map. The RMS gives the clinician an indication of the clinical effect the HOA have on the patients’ vision. In figure 5 we see a translation to the point spread function which may better illustrate the visual disturbance the patient may see at different pupil diameters. This enhances the clinicians capability of understanding the clinical implication of the HOA.

each refractive component of the eye can contribute to the HOA: the tearfilm, the anterior cornea, the posterior cornea, the crystalline lens, and even vitreous turbidity, and retinal thickness.

1.3.2 Wavefront technology in refractive surgeryIn standardized keratorefractive excimer laser procedures, the sphere and the cylinder are treated. The treatment of these refractive errors induces a change in the form of the cornea, and in some cases causes irregular astigmatism, HOA. The goal of wavefront based refractive surgery is to reduce existing aberrations, and possibly to reduce induction of aberrations.14 As a result we expect better unaided visual acuity,

figure 3: Plots of the values in the unit disk, representing the Zernike polynomials. For the clinician this is represented in color maps, which allow a pictorial representation of the HOA of the patients’ eye.

14

removed, the effect of the treatment of HOA is predicted and corrected for in the

ablation profile. 10

Figure 3: Plots of the values in the unit disk, representing the Zernike polynomials. For

the clinician this is represented in color maps, which allow a pictorial representation of

the HOA of the patients’ eye.

Figure 4 a, b, and c:

a) A color map of the total wavefront of an eye with a refractive error of S + 4.25 C –

3.50 x 100. b) A color map that shows the higher order aberrations only. c) A graphical

and numerical representation of the most important HOA that are used in refractive

treatments. In the above scans we see that there is a vertical coma (Figure 7b) that has a

numerical value of 0.76 micrometer (figure 7c). In the total aberrometry the vertical

coma is not visible, as the lower order aberrations in this eye are quite high (Figure 7a).

15


1

14

removed, the effect of the treatment of HOA is predicted and corrected for in the ablation profile. 10

Figure 3: Plots of the values in the unit disk, representing the Zernike polynomials. For the clinician this is represented in color maps, which allow a pictorial representation of the HOA of the patients’ eye.


a) A color map of the total wavefront of an eye with a refractive error of S + 4.25 C – 3.50 x 100. b) A color map that shows the higher order aberrations only. c) A graphical and numerical representation of the most important HOA that are used in refractive treatments. In the above scans we see that there is a vertical coma (Figure 7b) that has a numerical value of 0.76 micrometer (figure 7c). In the total aberrometry the vertical coma is not visible, as the lower order aberrations in this eye are quite high (Figure 7a).

14

removed, the effect of the treatment of HOA is predicted and corrected for in the ablation profile. 10

Figure 3: Plots of the values in the unit disk, representing the Zernike polynomials. For the clinician this is represented in color maps, which allow a pictorial representation of the HOA of the patients’ eye.


a) A color map of the total wavefront of an eye with a refractive error of S + 4.25 C – 3.50 x 100. b) A color map that shows the higher order aberrations only. c) A graphical and numerical representation of the most important HOA that are used in refractive treatments. In the above scans we see that there is a vertical coma (Figure 7b) that has a numerical value of 0.76 micrometer (figure 7c). In the total aberrometry the vertical coma is not visible, as the lower order aberrations in this eye are quite high (Figure 7a).

figure 4: a) A color map of the total wavefront of an eye with a refractive error of S + 4.25 C – 3.50 x 100. b) A color map that shows the higher order aberrations only. c) A graphical and numerical representation of the most important HOA that are used in refractive treatments. In the above scans we see that there is a vertical coma (Figure 4b) that has a numerical value of 0.76 micrometer (figure 4c). In the total aberrometry the vertical coma is not visible, as the lower order aberrations in this eye are quite high (Figure 4a).

contrast acuity and fewer side-effects in terms of night vision problems.13, 15-16 In wavefront treatments, we can treat the total of the HOA, but then again, new HOA are induced.15, 17 The treatment of HOA can result in overcorrections.15, 18 In state of the art laser treatments, wavefront-guided, or customized treatments are performed – these take into account the most important of the HOA and the effect that their treatment might have on the postoperative refraction and HOA. In this way visually disturbing HOA are removed, the effect of the treatment of HOA is predicted and corrected for in the ablation profile. 10

1.4 contrast sensitiVity

1.4.1 Quality of vision, snellen visual acuity, contrast sensitivity, wavefront technology, and straylightQuality of vision is difficult to define, and harder to measure in a repeatable and standardized manner. The Snellen acuity test tests spatial-resolving ability under high contrast circumstances. It is very sensitive to defocus, astigmatism, and HOA. Contrast sensitivity test is more dependent on the whole visual system depending on the precise version of the test, from the cornea, through the retina, and the visual pathways to the visual cortex, i.e. the whole physiological system.19 Aberrometry measures the optical quality in terms of spatial distortion of the wavefront. Straylight is another aspect of optical quality, measuring the optical quality of the eye due to light scattering dominating from 1 degree away from the center of the point spread function.

c

a b

16


1

1.4.2 background to contrast sensitivity testingThere are many factors in visual performance that relate to contrast sensitivity. If contrast sensitivity is lost, this may impair function like reading, finding objects, mobility, and driving.20-24 However, contrast sensitivity testing is always supplementary to visual acuity testing.25

Visual acuity, as measured under high contrast condition is but one way to describe visual quality. This is actually a spatial resolving power of vision, in which the smallest target is seen at high contrast. Campbell and associates found in the 1960-ies that for sinusoidal gratings humans see medium resolution targets best as compared to low or high resolution targets. This is called the contrast sensitivity function.26 Figure 6 shows the kind of gratings used for contrast sensitivity testing. A lot of contrast sensitivity tests have been invented, and attempts have been made to chart the differences in contrast sensitivity in different disease states, however no specific defect for a specific disease has been found.25 There are conditions like ageing, cataract, and other pathologies, in which we know that contrast sensitivity is decreased, but the testing for contrast sensitivity has little diagnostic value.25 The use of contrast sensitivity has played a role in the screening for glaucoma, but the low sensitivity and specificity of these tests have impeded the implementation of contrast sensitivity tests in clinical practice.27

The main problem with contrast sensitivity is that it is subjective and rather inaccurate. It complements other measurements of vision, like visual acuity and straylight, 5 but has little added value. Relevant to refractive surgery we know that refractive multifocal IOL’s cause a decrease in contrast sensitivity, especially under

15

Figure 5: The point spread function – the behavior of a point light, according to different

pupil sizes and the eyes’ higher order aberrations, represented in a way the clinician can

deduct the effect of HOA on vision.

figure 5: The point spread function – the behavior of a point light, according to different pupil sizes and the eyes’ higher order aberrations, represented in a way the clinician can deduct the effect of HOA on vision.

17


1 twilight conditions.28 This reduced contrast is because of the fact that there are 2 foci, of which one is in focus, and the other acts like a disturbing light screen and reduces contrast.

Contrast refers to the amount of lightness or darkness an object has in its surroundings. There are a lot of tests that were developed that test contrast sensitivity, since interest in this began in the 1960s.

Contrast sensitivity is defined as the inverse of the contrast value at threshold. Contrast sensitivity is plotted on a chart in which the x axis is the spatial frequency, and the y axis is contrast sensitivity in log scale. Spatial frequency is specified in cycles per degree (cpd), which corresponds to the spatial frequency of the sine wave grating in terms of size, using cycles per degree of visual angle as the unit. Maximal contrast sensitivity function is at 3 to 6 cpd. The curve of contrast sensitivity is bell shaped. At the high frequency end, where contrast sensitivity is lowest, 100% contrast is needed, it corresponds to visual acuity. Figure 6 shows a typical contrast sensitivity curve.

The complexity of different targets in day to day situations, and facial recognition have been studied.29 Military situations have also been extensively studied.5, 22 Road safety has been a major subject of testing contrast sensitivity function.23 One study showed that patients with visual acuity of 0.5 or worse due to cataracts, as a result of improved contrast sensitivity after cataract surgery, had half the rate of motor vehicle accidents, when compared to those who did not have surgery and still had their own crystalline lens.23 This was not corroborated by later studies.30

18

Figure 6: The contrast sensitivity curve (yellow line) is shown here superimposed upon a grating chart illustrating the gratings being used for contrast sensitivity testing. Contrast sensitivity = 1/threshold value for contrast visibility. To the left side contrast sensitivity is plotted on the vertical axis, on the right side the corresponding percentage contrast is plotted. The curve illustrated that Snellen acuity corresponds to the highest contrast (100%).

1.4.3 CONTRAST SENSITIVITY TESTING IN CLINICAL PRACTICE

The clinical use of contrast sensitivity can be in detection and monitoring of disease, and

in gauging the effects of therapeutic intervention. The therapeutic intervention can be

in the form of drugs, or new IOL technology, or even refractive surgery.

Several contrast sensitivity tests have been used: the Regan chart31, and the Pelli-

Robson chart32, the Holladay Contrast Acuity Test, and grating charts propagated by

different researchers19, 33.

Astigmatism, spherical blur, higher order aberrations, light scatter, and the retina-brain

system may cause disturbance of contrast sensitivity. As a result contrast testing,

figure 6: The contrast sensitivity curve (yellow line) is shown here superimposed upon a grating chart illustrating the gratings being used for contrast sensitivity testing. Contrast sensitivity = 1/threshold value for contrast visibility. To the left side contrast sensitivity is plotted on the vertical axis, on the right side the corresponding percentage contrast is plotted. The curve illustrated that Snellen acuity corresponds to the highest contrast (100%).

18


11.4.3 contrast sensitivity testing in clinical practiceThe clinical use of contrast sensitivity can be in detection and monitoring of disease, and in gauging the effects of therapeutic intervention. The therapeutic intervention can be in the form of drugs, or new IOL technology, or even refractive surgery.

Several contrast sensitivity tests have been used: the Regan chart31, and the Pelli-Robson chart32, the Holladay Contrast Acuity Test, and grating charts propagated by different researchers19, 33.

Astigmatism, spherical blur, higher order aberrations, light scatter, and the retina-brain system may cause disturbance of contrast sensitivity. As a result contrast testing, wavefront measurements, and straylight measurements complement each other, and enable the diagnosis of which element of the visual pathway causes a decrease in contrast.19 In the clinical situation the information obtained from contrast sensitivity testing is usually redundant, and not cost effective.25

1.5 straylight in refractiVe surgery

1.5.1 history and development of the concept of straylightBy definition of the Commission Internationale d’Éclairage (CIe) straylight is disability glare. Disability glare occurs when visibility is reduced when there are glaring light sources in the field of view.34 Straylight predicts the loss of retinal image contrast as a result of intraocular scatter.35 The first measurements of straylight in humans were done in the 1920-ies and 30-ies by Luckiesh, Holladay, and Stiles. Later studies resulted in the introduction of a straylight parameter.36 For a long time there was a discussion whether disability glare is an optical or a neuronal phenomenon.34

1.5.2 clinical value of straylightClinically straylight may produce complaints of hazy vision, loss of contrast and color saturation, difficulties with recognizing objects against light, and halos around bright light sources.36 Straylight has a negative effect on contrast sensitivity.36 Straylight and glare are the result of forward scatter, while the slit-lamp image relies on backscatter.37 So, in the patient with good Snellen acuity, and a normal slit-lamp examination, forward scatter can still cause clinically significant glare complaints, which we cannot diagnose using the traditional modalities.37 Therefore it can be concluded that straylight measurements significantly complement the clinical tests.

The point spread function (PSF) (see figure 7) describes the response of an imaging system to a point object. The point spread function enables us to understand the quality of the retinal image.38 Small changes in the PSF may cause severe visual disturbances. The PSF has a spatial domain, which is the horizontal axis, which is the angle of the visual input. It has a very steep peak with a very wide spread. (See figure 7). The tip of this peak is the 1 min of arc in which we test visual acuity. Clinically this can be in Snellen acuity charts, or with wavefront aberrometry, measuring HOA. The peak is around 1 min of arc or 0.02 degree. The vertical axis is the intensity domain. It is

19


1

logarithmic, and we see that the intensity is highest at the center at 0 degrees, and quickly decreases as it spreads out to 90 degrees. We measure visual acuity at the center core of the PSF.38 Contrast sensitivity is measured in a wider area of this core up to 0.3 degrees or 3 cpd, which is a little bit spread form the core. Straylight is measured more than 1 degree away from the central core of the PSF. Straylight does not contribute to VA or to HOA. The functional importance of straylight is in its relation to disability glare and visual complaints related.38

The clinical importance in measuring straylight is that it correlates weakly to visual acuity, and can explain visual complaints that are not measured by spatial resolution such as Snellen visual acuity testing.36, 39 The Snellen acuity, which tests high contrast small degree spatial resolution vision, can be very high, while the other aspects of the point spread function, that is straylight cause visual disability. This is explained by the fact that part of the light from the image of interest comes to a focused image, while part of the light is dispersed and forms a homogenously dispersed background. The severity of this loss of contrast depends on the illuminance ratio between the background and the image. For example when driving at night with oncoming traffic, this may cause blinding.36

There are many different tests for glare. According to the CIe definition glare disability is straylight. Actual glare tests come however in many forms. The relationship with the CIe definition is often unclear.40 The simplest glare test is a pen light, this is a cheap test, in which Snellen acuity is measured, while the patient is blinded by the light source form the penlight, but inaccurate because of pupil miosis and lack of

21

quickly decreases as it spreads out to 90 degrees. We measure visual acuity at the

center core of the PSF.38 Contrast sensitivity is measured in a wider area of this core up

to 0.3 degrees or 3 cpd, which is a little bit spread form the core. Straylight is measured

more than 1 degree away from the central core of the PSF. Straylight does not

contribute to VA or to HOA. The functional importance of straylight is in its relation to

disability glare and visual complaints related.38

Figure 7: Point-spread function (PSF) of the normal human eye according to the standard formulated for the CIE in 1999. When the eye looks at a point source, the actual light distribution spreads out over the full retina. Different domains of this distribution are indicated, dominating different aspects of visual function. The PSF has steradian–1 as unit, and integrates to unity (steradian to be used as variable of integration).

The clinical importance in measuring straylight is that it correlates weakly to visual

acuity, and can explain visual complaints that are not measured by spatial resolution

such as Snellen visual acuity testing.36, 39 The Snellen acuity, which tests high contrast

small degree spatial resolution vision, can be very high, while the other aspects of the

point spread function, that is straylight cause visual disability. This is explained by the

fact that part of the light from the image of interest comes to a focused image, while

part of the light is dispersed and forms a homogenously dispersed background. The

figure 7: Point-spread function (PSF) of the normal human eye according to the standard formulated for the CIE in 1999. When the eye looks at a point source, the actual light distribution spreads out over the full retina. Different domains of this distribution are indicated, dominating different aspects of visual function. The PSF has steradian–1 as unit, and integrates to unity (steradian to be used as variable of integration).

20


1standardization.41-43 Another glare test is with the brightness acuity tester. It is practical, but the validity of this test has been questioned.44 There are several other commercial devices which combine visual acuity testing with glare testing. From the available literature it is clear that most of these devices are not valid in testing for glare. Many glare tests show improving function under different conditions.40 The only device that excelled in evidence for validity and reliability in clinical tests, is the straylight meter.35 Clinical experience is still limited,45 but is rapidly expanding. The straylight meter has developed from the direct compensation method to the compensation comparison method. This change in methodology has enabled the development of a computerized test based on the psychophysical well-established forced choice principle. The patient looks in the device and is offered a flickering light ring. This light is scattered and perceived as a faint flicker in the center of the ring. A counterphase light is then presented, and this can silence the straylight flicker. The alternate forced choice help determine the amount of compensation light needed, and also the reliability of the test outcome. The test has an estimated standard deviation (eSD), which is an internal check for reliability of the measurement. A reliable test has to have eSD of less than 0.08 to 0.12 log units depending on the application.39

Clinically straylight in early cataract is important: the patient may be visually impaired, but pass all the spatial visual acuity tests.39 In our day to day life, this means there are quite a lot of drivers who should not be driving, based on their straylight measurements.45 As in all clinical tests, there needs to be a clear cut off between normal and abnormal and a low risk for false positives, that is classifying people as having disability glare based on the test results, while they actually are not visually impaired by glare. In order to have a straylight meter that gives reliable and repeatable results, that could, for example serve in regulations of drivers licenses, it was concluded that a forced choice test would contribute to this.45

For normal eyes, subtle anatomic factors that influence straylight measured, are the pupil size46, the color of the iris,47 the translucency of the sclera and eye-walls,47 the vitreous cavity and its contents, and the retina.36 It has been suggested that eyes with a longer axis, that is myopic eyes, have more straylight.48 Age is really important factor that goes with increased straylight. This is strongly correlated with cataract formation.40 It has been shown that the reliability of straylight measurements is not influenced by the patients age49, and that corneal light scatter is constant with age.40 In the normal young eye the cornea contributes about 1/3 of the total straylight, the lens contributes another 1/3.37 The iris, sclera, and retina contribute the remaining 1/3.34

Clinical situations in which disability glare is relevant are corneal opacities, be it by dystrophies, scars, contact lens wear or resulting from corneal refractive surgery.36, 50-51 In cataracts, or in pseudophakia glare is a known symptom. 42, 52-53 Myopia in itself is a reason for increased straylight.48 Rozema et al ascribed this to the possibility that most myopes were contact lens wearers48, and van der Meulen et al showed contact lens wear is related with an increase in straylight.51 Vitreous disturbances are potentially important (paper in preparation). In lamellar corneal transplantation procedures

21


1 pre-operative straylight level was predictive for surgical outcome. (IJe van der Meulen, submitted paper).

In cataracts disability glare is increased.39-40, 54 In pseudophakia with monofocal lenses straylight is often reduced to levels of younger people.39, 55 Straylight in pseudophakia is related to the size of the capsulorrhexis and amount of anterior capsular polishing.56 Pseudophakic patients seem to have higher straylight values under scotopic circumstances, mostly related to the size of the capsulorhexis.56-57 Straylight is also increased in posterior capsular opacification (secondary cataract) that may occur post-operatively and is often alleviated by doing a YAG capsulotomy.55

Nightvision problems and glare have been shown to cause a decrease in contrast sensitivity in the first generation multifocal diffractive intraocular lenses.28, 58-60 However, straylight correlated more with older age than with the monofocality or multifocality of the IOL.60 Aspheric and spheric IOL’s also do not show a difference in straylight.61 This is not surprising, as we know that the higher order aberrations are on a different part of the point spread function than the straylight. These results were corroborated in studies with newer design multifocal lenses that are of refractive and diffractive design, and of different materials (silicone or acrylic materials).62-64 Subjective reporting of glare experienced under all light conditions and at night is no reliable predictor for disability glare (straylight) measured.63

1.5.3 straylight in refractive surgeryIn refractive surgery forward and backward scatter have been studied. To organize these data, one must take into account the development and different techniques in refractive surgery. Current modes of corneal refractive surgery are mainly by ablating tissue, be it on the surface like in PRK and LASeK, or after a flap is cut, as in LASIK.

Radial keratotomy for myopia is a technique in which radial incisions are made into the peripheral and mid-peripheral cornea, at 85-90% depth of the cornea. These incisions heal and fill with plugs of epithelial cells, which cause the incisions to gap and thus change the corneal curvature. Actually we purposefully induce scarring in the cornea. Some of these scars can be in the pupillary opening, in mydriasis, like in night-vision conditions and causing complaints of glare and glare disability. In the PeRK study (Prospective evaluation of Radial Keratotomy study) no significant increase of subjective glare complaints was found.65 Decreased contrast was found in cases the incisions where within the central clear zone.66 Veraart showed that with the direct compensation method straylight was increased after radial keratotomy.67 The increase in straylight was related to the pupil diameter and not to the number of incisions.67

Also in excimer-laser assisted refractive surgery we may expect an increase in straylight. In surface ablations we expect tissue response with changes in cellular structure and organization.68-70 In LASIK the stroma of the cornea is cut, the corneal lamellar structure is disrupted, and after excimer tissue ablation the tissue surfaces are disrupted. So, also in LASIK we expect cellular and fibrillar changes.68-70

In photorefractive keratectomy (PRK), one would expect an increase in straylight, as the healing process within the cornea may contribute to this increase. In PRK an increase

22


1in straylight was found. This was time related, and decreased to pre-operative levels, except in eyes which developed severe haze.71 Harrison et al found that straylight did not increase at 1 month post PRK.72 The fact that there was no increase in straylight was attributed to a larger treatment zone of 6 mm, compared to a treatment zone of 5 mm in Veraarts’ study.71-72 Schallhorn showed straylight to be significantly increased at 1 month, and decrease to pre-operative levels at 3 and 12 months.73 He concluded that glare disability was transient.73 Only in an individual case was straylight increased in such a way, that the patient rejected treatment of the other eye.73 In other studies straylight was shown to initially increase and later decrease to pre-operative levels.74-75

In LASIK an increase in post-operative straylight would be expected, based on the incisive effect of cutting the LASIK flap, and the misalignment of the corneal collagen lamellae. Beerthuizen et al reported the first study on straylight after LASIK .76 At 1 month he did not find increased straylight in eyes that had either LASIK or PRK. The study did show that under individual circumstances straylight was increased. This was mostly related to microstriae or debris in LASIK, and haze in PRK.76 Vignal et al. studied straylight in PRK and LASIK.77 They showed that straylight was overall within the normal range in 79% of treated eyes, compared to 86% of untreated controls. This is the first study in which increased straylight was correlated to patient subjective glare complaints.77 In our study on myopic subjects we demonstrated that straylight actually improved in both LASIK and LASeK.78 This is possibly related to a change in corneal thickness.78 Contact lens use can increase straylight, especially the use of hard contact lenses.51 It was suggested that contact lens use pre-operatively may account for some of the decrease, but by protocol patients do not wear their contact lenses pre-operatively, for 2 weeks in the case of soft contact lenses, and for 10-14 weeks in the case of hard contact lenses.

Another study has shown straylight to decrease after LASIK by 0.11 log units, at 2 weeks post-operatively, but the decrease at 6 months of 0.06 log units was no longer statistically significant.79 Another study was done comparing straylight in eyes treated contra-laterally with LASIK and PRK. Also here no increase was found in straylight in both groups, up to 12 months.80 Rozema related a post-operative decrease in straylight after LASeK for myopia to pre-operative increased straylight from contact lens wear.81 With proper adherence to removal of contact lenses before measuring eyes for excimer laser refractive surgery (prevention of treating warpage related changes) one does not expect a pre-operative increase in baseline straylight alone from the wear of contact lenses. Maybe the fact that all these patients are myopic plays a more significant role after all.48

The discussion whether straylight decreases or increases after uneventful excimer laser corneal surgery is not over yet. It is my understanding, that up to now all data point to the effect that modern laser treatment does not increase straylight. Straylight is increased only if there is a specific cause for increasing glare in the eye, in the form of flap striae or debris under the flap in LASIK, or haze and scarring in LASeK and PRK, and causes that have yet to be elucidated. There is a good correlation between post-operative complaints of patients and increased straylight.77 The relation between

23


1 backscatter slitlamp findings and straylight is problematic – we don’t always have clinical findings that correlate.

Statements that night vision is severely impaired after corneal laser surgery, and hence should not be done, are contrary to the findings, both clinically, and also contrary to satisfaction analysis of patients. This is reminiscent of the dilemmas on compromise.82 Maybe a compromise of having better uncorrected visual acuity, at the possible price of some side-effects in some of the people treated, some of the time, is acceptable. These side effects may be disturbing only under very specific condition may be a good trade –off for some people, and not for other. This is where free choice after good informed consent comes into play.

1.6 Quality of Vision and patient satisfaction

1.6.1 concepts of quality of vision and correlation to patient satisfactionFor most ophthalmologists the standard used for assessing visual acuity is some sort of a visual acuity card, be it the Snellen chart, the eTDRS chart, or any variant thereof. A visual acuity under high contrast conditions may not always predict the quality of vision in terms of straylight, contrast acuity and sensitivity. Quality of vision measured by questionnaires give an impression of quality of vision as subjectively experienced by the patient. This can be quantified in QALY “quality adjusted life years” which tries to give a numerical equivalent to perceived quality of life.

Patient satisfaction responds not only to the surgical and numerical outcomes, but also to quality of life, and function as seen by the patient after surgery. Measuring patient satisfaction is problematic, because perception of quality of vision by the patients is subjective and influenced by the personality of the patient, levels of expectations, and surrounding factors, like information on internet sites, the “grape-vine” and other lay-talk. It has even been shown that patients who are dissatisfied with vision after LASIK, still would recommend having LASIK, so reported satisfaction is not necessarily a sufficient measure of quality of vision.83

One definition of patient satisfaction is the difference between the pre-operative expectation of the outcome and the actual post-operative outcome. This can be managed by communication: usually this is summarized as “under-promise and over-deliver”. Refractive surgeons manage their patients’ satisfaction actively.1 This process was learned through study of patient satisfaction.84 Refractive surgeons also learn to translate patient complaints into diagnostic and therapeutic solutions towards those complaints.85

1.6.2 patient satisfaction questionaires and their validityThere are different questionnaires for quality of vision. Some of these questionnaires like the “Activities of Daily Vision” and the VF-14 are specific for cataract patients.86 These questionnaires do not answer the specific demands of refractive surgery

24


1patients. Some questionnaires incorporate a global yes or no, and some questionnaires ask about aspects of the surgery – the procedure itself, the recovery, and the visual outcome and possible side effects. 84, 87-96 The NeI VFQ 25 questionnaire was developed to answer many questions about many ocular situations in a validated manner, but also in a manner that it is still applicable in the clinical setting.97 The assessment of the success of refractive surgery was basically only evaluated in terms of clinical criteria.88 In the mid-nineties the first articles that specifically mentioned patient satisfaction started to appear.92, 98-99 Questionnaires were formulated by clinicians, and the process of validation of their content came later.88 All the questionnaires also have different levels of sensitivity and specificity to the problem being assessed.3, 97 Questionnaires for cataract surgery and spectacle freedom are used in different settings97, 100, and translated, and then used, usually in a non-validated manner for assessment of visual function after implantation of multifocal IOLs.101 Another questionnaire developed was the Refractive error Correction Quality of Life Questionnaire (RQL).3 This was developed after the NeI VFQ 25 was found to be insufficient in answering quality of vision issues in refractive surgery.3 Recently, the validity of this questionnaire was tested. Ongoing insight into patient satisfaction measuring methods has shown that the modality tested, should be uni-dimensional. That is, one cannot derive one score, from more than one modality. In the case of the NeI VFQ 25 the modalities tested are visual function and quality of life, and these cannot be reported in a single score.102

The newest validated quality of vision questionnaire is a questionnaire that was validated for different types of surgery (from refractive surgery to cataract) and includes scales for frequency, severity, and how bothersome a symptom is.103

Some factors could be specifically linked to lower satisfaction after LASIK: increasing age of the patient, or flatter pre-operative curvatures, the need for enhancement procedures,104 and night vision problems.87 These night vision problems can affect night-driving.105 Some of the night vision complaints are caused by higher order aberrations, which may influence quality of vision.85 Newer diagnostic and interventional technology appears to improve these outcomes. For example: the larger optical zones used to prevent halos.106-107 As such, patient satisfaction and complaints can be analyzed and translated into technical and clinical improvements.

The most important factor that came out of these questionnaires is that the magnitude in terms of visual acuity and contrast sensitivity of the improvement after surgery is not a measure of its success. The functional improvement, as perceived by the patient, can be a measure of success of surgery.105

Outcomes of satisfaction questionnaires are even influenced by where the questionnaire is filled out, at the clinic or at home,88 or by the non-responders.97, 100, 104 So, the major obstacle remains, that satisfaction is a psychological phenomenon that is hard to gauge, and it has proven difficult, to say at least, to capture all modalities of quality of vision and refractive surgery in one single questionnaire.3 In my opinion, the use of objectively measurable parameters such as visual acuity, refractive error, and straylight allow for objectivation of the deviation are preferable to patient satisfaction questionnaires with their myriad confounding factors.

25


1 1.7 outcomes in corneal laser surgery

1.7.1 outcomes of standard laser treatment with first generation lasersConventional or standard laser treatment refers to the ablation of the spherocylindrical correction with the laser according to Munnerlyn’s formula.108 Conventional laser treatment of myopia induces positive spherical aberration proportional to the amount of myopia treated. 109 Outcomes of standard treatment for low to high myopia from early studies are summarized in table 2 and 3. Standard (or conventional) treatments have been reported to reduce contrast sensitivity.110-111

1.7.2 results with wavefront guided lasers and their relation to improved technologiesWith the advent of wavefront-guided laser treatment we see an overall improvement in percentages gaining uncorrected distance acuity of 0.5, 1.0 or better, improved

table 2: Outcomes of uncorrected visual acuity early studies on corneal laser surgery.

authors - year myopia % 1.0 or better % 0.5 or better refraction within 1.0d

Seiler112 1991 -4.50+ 1.00 D 48 96 92

MacDonald113 1989

-2.3 to -5.0 D 28 86 57

Salz114 1992 -1.75 to -5.00 42 92 92

Sher1151991 -4.00 to -12.00 19.3 45 55

Gimbel951993 -5.62 + 1.63(first eyes)

67.2 96.2 43

Gimbel95 1993 -4.96 + 1.48(2nd eyes after nomogram adjustment)

73.1 92.3 45.2

table 3: Outcomes of standard ablations for myopia with LASIK and PRK.

authors/ year myopia% 1.0 or better*

% 0.5 or better*

refraction within 1.0d

% of eyes with 2 lines lost**

el Danasoury, 1999116, Fernandez117, 2000, Tole118 2001

-2 to -6 67-86% 93-100% 94-100% 2.1%

Hersh119, 1998, Kawesh120, 2000, Pallikaris121, 1994

-6 to -12 26-71% 55-100% 41-96% 0-4.5%

Hersh119, 1998, Kawesh120, 2000, Pallikaris121, 1994

-12 26-65% 32-65% Up to 27%

* uncorrected distance visual acuity, ** best corrected distance visual acuity

26


1table 4: Outcomes of wavefront excimer laser treatments.

authors/yearmean myopia + sd

% 1.0 or better*

% 0.5 or better*

refraction within 0.5d

% of eyes with 2 lines lost**

Awwad et al126, 2004

-3.59 + 1.54 (LADARvision 4000)-3.62 + 1.46 (VISX S4)

NR

98

95

98

95

0

0

Durrie and Stahl127, 2004

-4.66 + 1.73 (LADARvision 4000)-4.382 + 1.71 (VISX S4)

93

90

100

97

83

93

0

0

Pop and Payette136, 2004

-4.0 (Nidek 5000-CATz)

92 100 85 0

Aizawa et al125, 2003

-7.30 + 2.72 77.9 96.5 77.3 4.5

Venter129, 2005 -3.72 + 1.96 100 88 92 4

* uncorrected distance visual acuity, ** best corrected distance visual acuity.

rates of reaching target refraction, and also decreased rates of loss of lines of CDVA (Table 4).122 For the first time there is a report that post-operative UDVA is better than pre-operative CDVA.123

Have treatments improved? The above tables show that from the very first publications of excimer laser treatments, predictability and visual acuity outcomes greatly improved.84,

95, 113-114, 124 13-15, 18, 85, 116-121, 125-132How have lasers improved over the years? The very first lasers were mostly broad-beam lasers, in which the cornea was ablated in a single pass. Problems then were caused by the ablated tissue which interfered with the rest of the laser beam application causing central islands. Cyclotorsion in supine position interfered with the effectiveness of astigmatic corrections.133-134 Centration of the treatment on the papillary axis or the center of the pupil have long been topics of discussions. Centration, especially with the newer ablation profiles that are wavefront-guided or optimized are very sensitive to centration on the visual axis.135 Newer laser systems, especially those with custom-capability have sophisticated eye-track systems. The tracking systems are usually a combination of passive trackers, that stop the laser ablation beam if the eye deviated from the operative field, and active eye-tracker systems, with infra-red cameras, which adjust the movement of the laser beam with the eye-movement of the patient.137 Parallax, that is the curvature with which the laser beam arrives at the ocular surface, is not corrected for, and this may change the effectiveness of the laser pulse, hence good fixation and centration remain the mainstay of a well applied laser treatment.138 Newer lasers using flying spots and smoother ablation profiles cause less haze and also less regression.139-140 Wavefront guided or wavefront optimized nomograms are based on wavefront measurements of the patients’ eyes. Wavefront ablation nomograms can also help save tissue, because less tissue is needed per diopter of defocus.130 This effect may be related to the specific laser used.

27


1 Wavefront-guided treatments had comparable predictability and safety to standard laser treatments, but patient satisfaction, specifically with night vision and night vision with glare was improved122. Higher order aberrations are still being induced, but in much less amounts than with conventional laser nomograms.17, 122 This effect is more pronounced if the pre-operative HOA are higher.17 Most adverse events remained the same as they were mostly related to microkeratome and flap events, and not inherent to problems with the laser ablation profile122. Data on accuracy of the treatment can be inferred from the retreatment rates, but these are not complete in most studies on standard treatments and on wavefront guided treatments.122 Contrast sensitivity was unchanged or slightly improved in all these studies.122, 127, 136, which is not surprising as we know that low contrast visual acuity is significantly correlated with HOA.141-142

1.7.3 improving outcomes by reducing side effects of wavefront based ablationsRecently more studies have shown that outcomes with the newer lasers are more accurate and reproducible (Table 5). Supervision defined as 2.0 Snellen acuity (or 20/10) is not reported often.13, 130

Wavefront optimized ablations are wavefront guided ablations, in which an attempt is made to preserve the cornea asphericity. It was found that for eyes with HOA of over 0.35 microm the wavefront guided ablation had a better result, than the wavefront optimized.143 The average cornea is prolate (spheroid in which the polar axis is greater than the equatorial radius), but the normal range is between mild oblate (spheroid in which the polar axis is shorter than the radius of the equatorial circle) to moderately prolate.144 even when trying to preserve the prolate shape of the cornea by using optimized ablation profiles, all treated eyes have a tendency toward an oblate shift.145 In a retrospective study of 160 eyes treated with an optimized ablation, post-operatively all eyes were between prolate and mildly oblate. However, there was no significant correlation between contrast sensitivity function and visual acuity and the corneal shape. They showed, that spherical aberration was the greatest predictor for contrast and glare abnormalities.146 Other studies comparing wavefront guided versus optimized treatments, have come to the conclusion that wavefront guided treatments decrease HOA and are associated with better contrast sensitivity.147

Millions of patients have been treated, mostly satisfactory with cornea laser surgery.144 The discussion about which ablation profile is best is not completely clear. Most improvements in technology arrived more or less simultaneously: iris registration technology, eye-tracker technology, ablation profile technology, it is very hard to discern, but there seems to be limited evidence that wavefront ablations achieve better outcomes.148

28


1table 5: Results of wavefront guided treatments.

author / year laser

fu in mths

n=eyes

pre-op se

post-op se +0.5d

ucda > 1.0

gain of ucValines (%)

Lee149 2006

VISX S4CustomVue

6 104 -4.08+ 0.31 -0.44+0.31 75

Awwad126

2004VISX S4CustomVueLADAR 4000CustomCornea

3 50

50

-3.59+1.55-3.16+1.63

-0.14+0.29-0.04+0.24

Nuijts130

2002Technolas 217z

6 6 -3.88+ 1.92 -0.06+0.41 92 67 16

Kim15

2004Technolas 217z

3 24 67

Brint132

2005LADAR 4000AllegrettoWave

3 30

30

-3.27

-3.67

93

90

80

90

Slade14

2004Alcon Custom corneaVISX CustomVue

1 25

25

-3.41

-3.34

-0.12+0.31

-0.40+0.40

92

72

76

56

0

0

Kohnen128

2004Technolas 217zZyoptix 3.17

12 97 -5.22+2.07 -0.25+0.43 77 83 5

Subbaram131

2007 Technolas 217 z APT

1 175 -4.89+2.06 -0.11+0.34 92 93

Mrochen13

2000Wavelight Allegretto

1 3 100 100 100

Lapid-Gortzak18

2008

Technolas 217zAPT

3 64 LASeK36 lasik

-3.77+1.57

-3.03+1.47

0.03+0.16

0.04+0.36

95

93

97

95

22

21

1.8 cataract surgery and refractiVe lens exchange

1.8.1 refractive lens exchangeRefractive lens exchange is the technique in which the lens preferably in presbyopic patients is removed and replaced by an intra-ocular lens. Since the advent of multifocal IOLs this can be offered as an elective refractive procedure.150 Patients opt for a form of freedom from spectacles for far and near vision. The outcomes in terms of unaided distance acuity need to be optimal. Residual refractive error need to be treated using methods available for refractive correction.151

In hyperopic patients this technique is least controversial as these patients have a relative lower risk of retinal complications than myopes. Corneal surgery and phakic

29


1 implantation surgery are less effective in treating hyperopic errors, because of the anatomic restrictions. Refractive lens exchange may solve the refractive error in a safe and predictable manner. 152

1.8.2 effect of refractive lens procedures on conventional cataract surgeryOn the one hand, one could state that the advent of refractive lens procedures has increased the demand for optimal refractive outcomes. On the other hand, the fact that the outcomes in refractive lens procedures are constantly being improved has also caused the demand for better outcomes in cataract surgery to increase. Basically, cataract surgery can no longer be seen as the removal of the cataractous lens and replacement with an artificial clear lens, but also as a refractive procedure, in which one strives for the optimal refractive outcome.

Were, until recently, decreased visual acuity coupled to patient complaints was the indication to perform a lens procedure, we now know, that visual quality also depends on objective visual quality parameters such as straylight, which when increased, can be a viable clinical indication to perform cataract surgery even when Snellen acuity is 1.0 or better. Amesbury et al showed in their study that patients who were operated for cataract with a 20/20 (1.0) visual acuity based on subjective complaints of glare and questionnaire results, had improved post-operative results based on subjective criteria, even though their pre-operative visual acuity of 20/20 is generally considered good vision.153 We clearly see that the attention to indications for cataract surgery is shifting: a decreased visual acuity is an arbitrary and insufficient descriptor of visual disability. Straylight is a complementary descriptor of visual quality. With increased straylight, even in the absence of decreased visual acuity, there is an indication for performing a lens procedure; with the new development of straylight measurement this aspect of visual function should be added as an objective criterion in the clinical setting in cases were patient complaints do not correspond to visual acuity.

1.8.3 multifocal intraocular lensesUntil recently, implant lenses were monofocal lenses. In these lenses there is one focus, set at the focal plane of the IOL used. Most patients need additional correction in glasses or contact lenses to be able to read or see at intermediate or far distances, because mainstream cataract surgery has the alleviation of the lens opacity as its goal, and the refractive outcome is secondary. Multifocal lenses have more than one focus, and thus enable both far and near vision without the need for additional optical correction. There are different designs of multifocal lenses. Those can be made of different materials including silicone, acrylic hydrophobic materials, to acrylic hydrophilic lenses, and combinations of material in between. The most commonly used are of the type in which refractive or diffractive rings within the optic divide the light for vision to a distance vision focus and a near vision focus. The distance between the different rings and the form of the rings on the optic can be different. IOL’s with rings , which alternate distance and near vision in their correction, are called

30


1refractive multifocal lenses. When the difference in the near and far foci is achieved by using diffraction, the lens becomes a diffractive IOL. When the rings have decreasing effect from the center to the periphery of the lens these lenses are called apodized lenses. This principle allows for better differentiation of the near and far foci, and as a result less light is lost to the near focus in case of low light conditions. . They are not effectively multifocal lenses, but they do have 2 main foci, which makes them actually bifocal with little depth of field. Theoretically and clinically diffractive IOL’s perform better for near than refractive IOL, while the distance vision is comparable.154-156

These lenses give side effects as a result of the existence of a secondary focus in the optic. The secondary focus causes a ‘blur circle’ on the retina. This may cause complaints of a shade or a blur and may cause complaints of seeing ‘halos’ and other dysphotopsias.157 The success of these lenses lies in the motivation of the patient to be spectacle independent, and the ability to resist the side effects of these lenses.157

Other types of lenses are those that mechanically change as a result of an accommodative effort. For example double hinged lenses, in which the optic is monofocal but is supposed to move with the capsular bag during an accommodative effort after the crystalline was removed.158 Other lenses are designed with two optics in which the compression at the equator of the lens capsule moves the 2 optics apart during accommodation and thus the focal length is changed, and between 4 and 7 D of accommodation can theoretically be achieved.159 The clinical outcomes of single and dual optic pseudo-accommodative IOL’s is controversial. In the FDA studies lenses like the Crystalens (Bausch and Lomb) model AT-45 IOL showed some improvement of near visual acuity.158 Patel et al showed that there was almost no effect on near visual acuity with this lens.160 Most studies show that the accommodation span of these lenses is clinically not sufficient. However Leydolt has shown that motivation for intermediate visual acuity can give a pseudoeffect in achieving that visual acuity, even when the patient has a monofocal IOL.161

1.8.4 results with multifocal iolsThe most studied and up to now clinically effective lenses are of the refractive and diffractive type. Their use has been proven to be effective and safe.162-165

However, patient satisfaction clearly depends on outstanding refractive results post-operatively. Patient selection, astigmatism control, careful biometry, and precise IOL calculation are factors that enhance patient outcomes.166-168 Steinert has shown that bilateral implantation with the Array multifocal implant as opposed to unilateral implantation of a multifocal IOL, increases the percentage of reading without glasses from 53-58% to 81%.169

Primary outcomes after multifocal lens implantation are the distance uncorrected and corrected visual acuity, the near visual acuity, and spectacle independence. Secondary outcome measures are the depth of field, contrast sensitivity, glare, subjective assessment of quality of life or visual function, and surgical complications.

In the 1990-ies the first generation of multifocal diffractive IOL’s caused side effects in significant numbers.58, 170-172 Second generation multifocal diffractive IOL’s

31


1 have better results, and may sometimes outperform refractive IOL’s for near visual tasks.173-174 Still, success of multifocal implants is probably mostly related to motivation of the patient.152, 162 Newer lenses have modifications in their form, such as aspheric prolate anterior surface, lens edge changes, and placement of the diffractive rings on the posterior surface, which may reduce spherical aberrations, and improve mesopic contrast sensitivity.175-177 Multiple studies have shown that multifocal IOL’s produce a higher quality of life, spectacle independency in a high percentage of patients, with acceptable unwanted photic phenomena, and also lower contrast sensitivity.101, 178-179

1.8.5 the future of multifocal iols and cataract surgeryThe demand for refractive lens surgery will, in my opinion, increase because of increasing demands for spectacle freedom, and with increasing public knowledge of what can be achieved with cataract and refractive surgery. Refractive surgery will cause technical improvements to be implemented in cataract surgery. Again, the benchmark will, in my opinion, move away from posterior capsular break, and gross complications, to outcomes in terms of refractive outcomes and patient satisfaction.

In medical indication in cataract surgery until now, patient complaints of decreased vision, coupled to decreased visual acuity is the most widely accepted indication to perform cataract surgery. Advances in understanding, that increased straylight with age is mostly related to the development of cataract, and that this can occur with a visual acuity of 1.0,39 will most probably also lead to a change in indication to perform cataract surgery, based on the addition of this new objective parameter for visual quality.

1.9 outcomes in bioptics

1.9.1 definition and practice of biopticsThe term bioptics is used for different types of refractive combined procedures. The term most probably stems from doing two refractive (optical) procedures consecutively in a single eye. In 1995 Maloney published the results of PRK in a few eyes that had residual myopia after cataract surgery, within a larger study of the results of PRK in myopia.180 The term was coined in 1999 by Zaldivar to describe the use of an additional refractive procedure on the cornea after target refraction was not achieved with a phakic lens implantation.181 Some define bioptics when the LASIK flap is cut before the lens procedure and lifted when the enhancement is needed.151 Since, it has been expanded to the definition in which we now use it, which more broadly encompasses any refractive surgery procedure in which more than one type of surgical technique is used. Bioptics is also a solution in those cases in which the magnitude of the refractive error exceeds the corrective range of any of the existent refractive procedures. The second procedure extends the corrective measure to the one that is necessary to achieve target refraction. The combined procedure can include a phakic lens implantation which includes an expected or unexpected residual error which can then be corrected in the corneal plane with any of the above mentioned

32


1technologies. 182 The procedure can include LASIK with incisional corneal astigmatic corrections,183or a combination with phakic IOL implantation with LASIK and PRK. 184-186 The combination of refractive lens exchange, also known as clear lens exchange with ensuing LASIK or LASeK correction for either hyperopia or myopia.187-189 Cataract surgery with residual refractive errors and subsequent LASIK and LASeK procedures have been published.190-192 Leccisotti used bioptics to achieve 3 goals: a. treating large refractive errors by a sequential method, usually a lens related procedure followed by a corneal procedure, b. improving stability and predictability of the refractive outcomes, c. maintain a state of minimal induction of higher order aberrations, i.e. ensure that HOA stay as low as possible.193

Correction of the untreated corneal astigmatism or residual refractive error enables adjustment and correction of the final outcome of these pseudophakic multifocal patients. These refractive surgery procedures give safe and predictable results 33,180,

184-185, 188-194 168, 195-196 197 Table 6 summarizes the published results of bioptics.

1.9.2 safety and predictability of biopticsA major concern is that these patients tend to be older, and as such may be more prone to complications. Corneal refractive surgery, according to the literature should be performed 6-12 weeks after the lens procedure, to allow for wound and IOL stabilization, and allow subclinical corneal edema to dissipate.151 More epithelial defects, and more epithelial ingrowth have been observed, as has the incidence of Diffuse Lamellar Keratitis of up to 15%.197 Other authors reported extremely low complication rates.173, 187, 190-193, 198 In our series the main adverse event has been residual refractive error or not effective enough laser treatment in about 7 % 199. LASIK was as safe as LASeK in our hands in the groups that we treated. Haze, which has been reported by Maloney to have been around 8% is most probably less frequent because of better ablation profiles with newer lasers.180

table 6: Outcomes of corneal refractive surgery in monofocal pseudophakic patients.

author / yearn=(eyes) surgery

sepre-op

sepost-op fu

Within 1 d Within 0.5 d

Zaldivar181

199955 LASIK -2.61 +0.09 1m-4y

Kim191 2005 19 LASIK 100 83.3 myopes90.9 hyperopes

Ayala190 2001 22 LASIK -2.90 + 1.80 0.4 + 0.6 12m 81.8

Norouzi197 2003 20 LASIK 2.19 + 0.88 -0.32+ 0.34 6m 100 85

Artola195 1999 30 PRK -5.00+ 2.5 -0.25 + 0.5 12m 90

Pop189 2001 3134

PRKLASIK

-3.78+ 2.11-2.25 + 1.37

7583.3

41.783.3

Kuo192 2005 11 LASIK PRK

-3.76 + 2.50 -0.88+ 1.43 12.2m

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1 1.9.3 outcomes of bioptics in patients with presbyopia correcting lensesResidual refractive errors after multifocal lens implantation are the main reason for patient dissatisfaction post-operatively.200 There are not many studies showing data of excimer laser procedures following multifocal lens implants. In most studies the use of the ablation nomogram is not specified, and standard treatments ( that is spherocylindrical treatments) as well as wavefront based treatments are used and analyzed together.201-202 Jendritza et al describes the use of wavefront treatments and concludes that it is a safe treatment for the refractive error, but that higher order aberrations do not improve. They found that wavefront could not reliably be measured. Wavefront treatment does have the advantage of iris registration and the possibility of correcting for possible IOL decentration and secondary refractive error, but the HOA mostly increased post-operatively. 203 Table 7 summarizes the results of bioptics in multifocal IOLs.

1.9.4 bioptics and wavefront technologyMost IOL’s change the HOA. Some HOA, like negative spherical aberration enhance depth of focus, at the cost of other aspects of quality of vision. Some IOL’s correct for spherical aberrations. Another aspect is that a wavefront guided treatment may remove HOA that actually enhance quality of vision. This is an unwanted side-effect.10 Another issue with wavefront measurements, is the fact that the IOL optic is 5-6 mm in diameter, depending on what kind of multifocal IOL is used. If the lens is decentered, or the pupil is wider than the optic when the measurement take place, aberrations

table 7: Outcomes of laser refractive surgery in multifocal pseudophakic eyes:

author yearn=(eyes) surgery

sepre-op

sepost-op fu

Within 1 d

Within 0.5 d

Leccisotti196

200418Array

PRKStandard

1.28 +0.74 0.33 +0.27 100 83

Moftuoglu201

200985ReSTOR

Femto LASIK standardWavefront

-0.34 +0.9 -0.07 +0.29 6m 99% 96%

Jendritza203

200820Tecnis

LASIKWavefront

1.06 +0.77 -0.03 +0.28 3m

Jendritza203

20084ReSTOR

LASIK Wavefront

0.75 +0.56 0.13 +0.22 3m

Jendritza203

20083ReZoom

LASIKWavefront

0.08 +1.2 0 + 0 3m

Alfonso204

200853 Femto

LASIKStandard

0.2 + 0.49 0.014 + 0.0170 6 100% 96.2%

Lapid-Gortzak199 2010

18ReSTOR

LASIKStandard

0.50 +0.72 0.29 +0.34 3 m 100% 88%

Lapid-Gortzak199 2010

27 ReSTOR

LASeKStandard

0.34 +0.73 0.21 +0.13 3 m 100% 78%

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1coming from the optic edge and beyond, are translated in the treatment as HOA that are treated centrally on the cornea. We have performed wavefront guided LASIK in multifocal and monofocal IOL’s with unsatisfying results in terms of uncorrected visual acuity (UCVA) and residual refractive error, and as a result have abandoned this practice (Lapid-Gortzak, unpublished data.).

Lessicotti showed the results of PRK for residual ametropia after refractive lens exchange with the Array multifocal IOL. He showed that this was effective in treating the refractive error, but that this had no effect of dysphotopic complaints.196 Alfonso et al. show that standard femtoLASIK treatment for residual ametropia is safe and predictable.204

1.9.5 conclusion on biopticsFrom the available literature it seems that bioptics is a viable option for residual refractive error after IOL implantation, irrespective of whether the IOL is monofocal or multifocal. The technique is still evolving in terms of indications and preferable technique utilization.151

1.10. complications and management of com-plications in refractiVe surgery

1.10.1 how often do complications occur in refractive surgery and what are their clinical implications?Complications in refractive surgery are feared by both patients and surgeons. The definition of a complication from the patients’ perspective is any result that deviates from the patients expectations. From the surgeons’ point of view it is any result that fails to achieve the planned refractive target, a complication leading to severe visual loss, or chronic complaints. There are no accurate estimates of complications, because of the lack of clear and universally accepted definitions of complications.205 Fortunately serious side effects leading to severe visual loss are rare.205 There are reports from about 10 years ago that estimated the incidence of complications in LASIK to around 5%.206 207 More recent reports have shown a significant decrease in the incidence of complications to 0.02%-1.5%.6

Looking at meta analysis of corneal laser surgery, we see that patient satisfaction rate for myopic LASIK is around 95.4% and for hyperopic treatment satisfaction rate is 96.3%.208 The 1 in 20 patients who are not satisfied, are so because they did not achieve the expected refractive outcomes or have bothersome side-effects.

The most common cause for dissatisfaction is a residual refractive error.205, 209 Despite the fact that it is not a severe complication, it leads to enhancement (refractive surgeons‘ euphemism for retreatments) and more prolonged recovery time till the target is achieved.

Levinson et al analyzed the reasons patients seek a second opinion after refractive surgery procedures. The foremost reasons were residual refractive error, dry eyes,

35


1 redness or pain in the eye, and glare and halo complaints.210 Note that none of these complaints are actually caused by vision threatening complications.

Severe or blinding complications occur rarely, but have a great impact on our patients.205 In LASIK these are mostly flap related; iatrogenic ectasia, infections, incomplete flap, traumatic flap problems, striae, diffuse lamellar keratitis, epithelial ingrowth and flap melts. In LASeK, PRK and surface ablations, complications are mostly related to healing and to infections. LASeK has a lower incidence of serious complications.

1.10.2 the most common complication: dry eyesDry eyes is the most common complication after both LASIK and surface ablation.211-212 The corneal nerves are ablated by the excimer laser. Regeneration has been shown to be aberrant, but protective function is regained. The best way to prevent this complication is by not treating patients whose tear film is insufficient. This is done by meticulous pre-operative diagnosis of the tearfilm production and function as given in treatment guidelines by peer groups.205, 213 It has been shown that the symptoms improve with time. Treatment consists of lubrication, and when necessary punctual occlusion with plugs or cautery, and sometimes by the use of Cyclosporin eyedrops or autologous serum eyedrops.214-216

1.10.3 complications in lasikMost complications are microkeratome related. These are the flap-cutting related problems, and the secondary ectasia problems. Other potentially serious complications include infection, diffuse lamellar keratitis, and epithelial ingrowth.

1.10.3.A Flap related problemsThe flap related problems, are related to microkeratome malfunction. This causes the cut of the corneal lamella to be incomplete, or buttonholed. The literature shows that there is a learning curve in cutting flaps.207 Stulting et al reported that in the first 1000 LASIK flaps, 2.7 % had flap-related complications.206 Gimbel et al reported that the incidence decreased from 4.5% in the first 100 flaps cut, to 0.5% in the last 200 cases of the first 1000 cases.207 A later study showed an incidence of 0.68% of flap complications.217 In these cases the procedure should be aborted, the flap allowed to heal, and after that another procedure can be considered. Based on surgeons experience and preference this can be another LASIK procedure or the safer surface ablation approach.205

1.10.3.B Secondary ectasiaSecondary ectasia occurs when the residual stromal bed is too thin, and the cornea is under biomechanical pressure, bows forward. This causes irregular astigmatism, severe visual loss, and sometimes corneal transplantation is needed to try and solve the problem. Iatrogenic ectasia is more common to LASIK. It can rarely occur in PRK and LASeK, but this has only been reported in eyes that have had a forme fruste keratoconus to begin with.218-219

36


1Secondary ectasia can be avoided in some cases. Accurate topography and pachymetry and analysis of these measurements can help avoid treating these patients. The use of thinner flaps may leave more residual stromal bed thickness. By calculating the minimal RSB thickness, at 300 microns instead of 250 micron, which is the minimum according to the literature. Patients at risk need to be detected pre-operatively. This pre-operative diagnosis is called forme fruste keratoconus. This is a very frustrating situation, because there are no absolute diagnosis parameters. At this point diagnosis is based on anterior and posterior corneal surface parameters, and their relative changes form the center of the cornea to the periphery coupled to a high index of suspicion. In the literature there are scoring methods for the relative risk. The relatively new process of post-publication peer review on these already published data and analysis of this literature have brought about a discussion on how to prevent secondary ectasia, at high sensitivity and specificity, without preventing refractive surgery because of false positives in our screening procedures. 220-222 Besides better understanding and diagnosis of which patient might be at risk for ectasia, moving away from LASIK technology to surface ablations, using thinner LASIK flaps, and calculating thicker stromal residual beds have been the modalities in which the prevention of secondary ectasias has developed.

1.10.3.C InfectionInfection after LASIK is a rare and sometimes severe complication. It is different from infective keratitis in non-LASIK corneas, because the flap offers physical protection to relative non-pathogenic pathogens, and this causes a more indolating infection which is hard to diagnose and eradicate. Pre-operative control of infection and sterility contribute most probably to the low incidence of infective keratitis after LASIK.

Reactivation of old infections, such as is the case in herpetic eye disease is an entirely different problem. Herpetic eye disease starts with a primary infection which is often asymptomatic.223 This explains why sometimes the patients (and their surgeons) don’t even know that they are at risk for a recurrence. The exact triggers for herpetic reactivation are unknown. Suggested triggers are stress, UV radiation, and surgical trauma. The excimer laser wavelength of 193 nm is close to the UV range, and could be such a trigger. Asbell has shown that deepithelialization of the cornea alone, like in surface ablations, is not a sufficient trigger for reactivation of herpes.223 The use of an excimer laser is, and can be suppressed by prophylactic antviral therapy.223 Herpetic eye disease is considered a relative contra-indication for corneal refractive surgery. It encompasses the risk of reactivation of active viral replication, but also of immune-mediated keratitis which in the end leads to scarring and corneal deformation and unexpected refractive outcomes secondary to corneal irregularities224, and even corneal perforation.225 Sometimes the visual disability from an herpetic corneal scar can be very disturbing to patients. In the well-motivated patient, under maximal anti-viral prophylactic coverage, both PRK and LASIK have been shown to improve vision in terms of scar tissue removal and refractive error correction.226

37


1 1.10.3.D Diffuse lamellar keratitisDiffuse lamellar keratitis is the sterile intra-lamellar inflammation that can develop starting 8 hours after the procedure. This is mostly an acute inflammation. Some of the risk factors, like autoclave biofilm with exotoxins, powdered gloves, certain LASIK blades, meibomian gland dysfunction and its’ secretion are known. Others are not. Prevention, like with any complication is the best solution. DLK comes in 4 stages, of which stage 1-2 need thorough follow up and intervention with steroid eye-drops only, while stages 3-4 need surgical intervention in the form of flap relift, rinsing the inflammatory debris between the flaps, and repostion the LASIK flap. Untreated severe DLK may lead to crinkles in the flap and flap melt and severe visual loss, or to epithelial ingrowth.

1.10.3.E Epithelial ingrowthepithelial ingrowth is when the corneal epithelium grows under the lamellar flap. The incidence is between 1-20% of surgeries. Most of cases are self-limiting, and need no intervention. In 1 to 1.7% epithelial ingrowth is persistent, reaches the optical axis, and may rarely cause decreased vision by direct obscuration of vision or more often decreased visual acuity secondary to flap surface deformation and irregular astigmatism. These are also the indications for surgical removal of the epithelial ingrowth.227-229 The incidence of epithelial ingrowth has decreased with better blade technology, and smoother flap edges227, but in cases of relift of flap that have been cut several years ago, the incidence may be as high as 30-40%.230 We show in our article that the effect of the epithelial ingrowth is not only on the flap surface and refractive error, but also in terms of disability glare, as measured by improved straylight after removal of epithelial downgrowth.231

1.10.4 complications in lasek and prk

1.10.4.A Delayed surface healingDelayed healing and irregular healing is sometimes seen in patients with insufficient tear secretion, overuse of topical anesthesia, use of mitomycin C.232 Diabetic patients or patients with other autoimmune disorders show more problems with delayed surface healing.232 Generally this is associated with more haze and regression and surface irregularity.

1.10.4.B HazeHaze occurs when ablation depth is deeper, in higher settings of myopia. It is known to start at around 1 month, and usually peaks by 3 months and usually abates by 6 months.232It is dependent on the quality of the laser beam, but also on external factors like exposure to sunlight. Fibrocyte migration caused by cytokines like tumor necrosis factor alpha, and transforming factor beta, cause fibrosis and scarring.233

1.10.4.C InfectionInfectious keratitis may complicate surface ablation, especially before complete wound closure. Infection after surface ablations usually is caused by Gram positive

38


1bacteria, Gram negative organisms, and rarely also by opportunistic organisms like Mycobacterium chelonae.234 Sterile infiltrates can sometimes be seen. This is associated with the use of non-steroidal anti-inflammatory eye drops.235 The most important differential diagnosis of sterile infiltrates is bacterial keratitis. Infection can lead to severe visual loss and needs to be diagnosed and treated. Sterile infiltrates usually dissipate with corneal healing and use of steroid drops after the epithelium has closed.

1.10.5 complications in refractive lens proceduresIn refractive lens procedures besides the residual refractive error, glare and halo complaints, any complications associated with an intra-ocular procedure can occur, but does so rarely. The most feared complication being an endophthalmitis: this has an incidence of 0.4% after cataract surgery in the Netherlands, according to the 2009 Cataract Surgical Practice Survey. Retinal detachment is the other major threat for vision. The recent literature has shown that myopia, younger age, longer axial length of the eye, male gender, and absence of posterior vitreous detachment are risk factors for retinal detachment in this type of surgery.236

1.11 aims of this study

Refractive surgery is a rapidly developing field, which encompasses many techniques that are widely practiced. Most technology is well-described in peer-reviewed literature. However there are still data missing. In this study we try to investigate several aspects of refractive surgery that are relevant in the current state of the art in this field of surgery.

The first aspect is the improvement in terms of reducing refractive error and improving Snellen visual acuity. Do wavefront optimized laser nomograms improve vision and decrease unwanted side-effects? As to bioptics: what is the minimal refractive error that can be safely treated, and is a standardized ablation or a wavefront ablation pattern the best way to achieve emmetropia?

The second aspect is investigation of quality of vision, defined by straylight. Does straylight, a parameter for quality of vision, change in corneal laser surgery? Are there differences between myopic and hyperopic treatments?

The third and last aspect in this thesis is the effect of adverse events and their treatments on Snellen visual acuity and quality of vision. Adverse events are a major concern in refractive surgery. It is impossible to broadly discuss rare events and their effect. We investigated the effect of epithelial ingrowth on straylight, and more importantly, the consequences of removal of ingrowth on straylight and visual acuity. Incidence and treatment effect of specific complications are investigated.

39


11. McGhee CN, Craig JP, Sachdev N, Weed

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202. Pinero DP, espinosa MJ, Alio JL. LASIK Outcomes Following Multifocal and Monofocal Intraocular Lens Implantation. J Refract Surg 2009:1-9.

203. Jendritza BB, Knorz MC, Morton S. Wave-front-guided excimer laser vision correc-tion after multifocal IOL implantation. J Refract Surg 2008;24:274-9.

204. Alfonso JF, Fernandez-Vega L, Montes-Mico R, Valcarcel B. Femtosecond laser for residual refractive error correction after refractive lens exchange with multifocal in-traocular lens implantation. Am J Ophthal-mol 2008;146:244-50.

205. Sugar A, Rapuano CJ, Culbertson WW, et al. Laser in situ keratomileusis for myopia and astigmatism: safety and ef-ficacy: a report by the American Acad-emy of Ophthalmology. Ophthalmology 2002;109:175-87.

206. Stulting RD, Carr JD, Thompson KP, War-ing GO, 3rd, Wiley WM, Walker JG. Com-plications of laser in situ keratomileusis for the correction of myopia. Ophthalmology 1999;106:13-20.

207. Gimbel HV, Penno ee, van Westenbrugge JA, Ferensowicz M, Furlong MT. Incidence and management of intraoperative and early postoperative complications in 1000 consecutive laser in situ keratomileusis cases. Ophthalmology 1998;105:1839-47; discussion 47-8.

208. Solomon KD, Fernandez de Castro Le, Sandoval HP, et al. LASIK world literature review: quality of life and patient satisfac-tion. Ophthalmology 2009;116:691-701.

209. Varley GA, Huang D, Rapuano CJ, Schall-horn S, Boxer Wachler BS, Sugar A. LASIK for hyperopia, hyperopic astigmatism, and

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1mixed astigmatism: a report by the Ameri-can Academy of Ophthalmology. Ophthal-mology 2004;111:1604-17.

210. Levinson BA, Rapuano CJ, Cohen eJ, Hammersmith KM, Ayres BD, Laibson PR. Referrals to the Wills eye Institute Cor-nea Service after laser in situ keratomi-leusis: reasons for patient dissatisfaction. Journal of cataract and refractive surgery 2008;34:32-9.

211. Battat L, Macri A, Dursun D, Pflugfelder SC. effects of laser in situ keratomileu-sis on tear production, clearance, and the ocular surface. Ophthalmology 2001;108:1230-5.

212. Benitez-del-Castillo JM, del Rio T, Iradier T, Hernandez JL, Castillo A, Garcia-Sanchez J. Decrease in tear secretion and corneal sensitivity after laser in situ keratomileusis. Cornea 2001;20:30-2.

213. NGRC. http://www.oogheelkunde.org/professionals/evidence-based-richtlijnen/item?urlProxy=/patienten/patientenvoor-lichting/richtlijnen2/consensus-refractie-chirurgie-2009&objectSynopsis=#96oYeANee6OoaSeMfu79Sg. 2009.

214. Wilson Se. Laser in situ keratomileusis-induced (presumed) neurotrophic epi-theliopathy. Ophthalmology 2001;108: 1082-7.

215. Noda-Tsuruya T, Asano-Kato N, Toda I, Tsubota K. Autologous serum eye drops for dry eye after LASIK. J Refract Surg 2006;22:61-6.

216. Salib GM, McDonald MB, Smolek M. Safety and efficacy of cyclosporine 0.05% drops versus unpreserved artificial tears in dry-eye patients having laser in situ keratomileusis. Journal of cataract and re-fractive surgery 2006;32:772-8.

217. Tham VM, Maloney RK. Microkeratome complications of laser in situ keratomileu-sis. Ophthalmology 2000;107:920-4.

218. Reznik J, Salz JJ, Klimava A. Develop-ment of unilateral corneal ectasia af-ter PRK with ipsilateral preoperative forme fruste keratoconus. J Refract Surg 2008;24:843-7.

219. Malecaze F, Coullet J, Calvas P, Fournie P, Arne JL, Brodaty C. Corneal ectasia after photorefractive keratectomy for low myo-pia. Ophthalmology 2006;113:742-6.

220. Randleman JB. evaluating risk factors for ectasia: what is the goal of assessing risk? J Refract Surg 2010;26:236-7.

221. Binder PS, Trattler WB. evaluation of a risk factor scoring system for corneal ectasia after LASIK in eyes with normal topogra-phy. J Refract Surg 2010;26:241-50.

222. Belin MW, Ambrosio R, Jr. Corneal ectasia risk score: statistical validity and clinical relevance. J Refract Surg 2010;26:238-40.

223. Asbell PA. Valacyclovir for the preven-tion of recurrent herpes simplex virus eye disease after excimer laser photok-eratectomy. Trans Am Ophthalmol Soc 2000;98:285-303.

224. Levy J, Lapid-Gortzak R, Klemperer I, Lif-shitz T. Herpes simplex virus keratitis after laser in situ keratomileusis. J Refract Surg 2005;21:400-2.

225. Perry HD, Doshi SJ, Donnenfeld eD, Levin-son DH, Cameron CD. Herpes simplex re-activation following laser in situ keratomi-leusis and subsequent corneal perforation. CLAO J 2002;28:69-71.

226. Kaufman SC. Use of photorefractive kera-tectomy in a patient with a corneal scar secondary to herpes zoster ophthalmicus. Ophthalmology 2008;115:S33-4.

227. Jun RM, Cristol SM, Kim MJ, Seo KY, Kim JB, Kim eK. Rates of epithelial ingrowth after LASIK for different excimer laser sys-tems. J Refract Surg 2005;21:276-80.

228. Latkany RA, Haq Fe, Speaker MG. Ad-vanced epithelial ingrowth 6 months after laser in situ keratomileusis. Journal of cata-ract and refractive surgery 2004;30:929-31.

229. Jabbur NS, Chicani CF, Kuo IC, O’Brien TP. Risk factors in interface epithelialization after laser in situ keratomileusis. J Refract Surg 2004;20:343-8.

230. Donnenfeld eD, and Solomon, K. Panel dis-cussion on controversies in refractive sur-gery. ASCRS, Boston, April 3-7, 2010 2010.

231. Lapid-Gortzak R, van der Meulen I, van der Linden JW, Nieuwendaal C, Mourits M, van den Berg T. Straylight measurements before and after removal of epithelial in-growth. Journal of cataract and refractive surgery 2009;35:1829-32.

232. O’Keefe M, Kirwan C. Laser epithelial keratomileusis in 2010 - a review. Clin ex-periment Ophthalmol 2010;38:183-91.

233. Leonardi A, Tavolato M, Curnow SJ, Freg-ona IA, Violato D, Alio JL. Cytokine and chemokine levels in tears and in corneal fi-broblast cultures before and after excimer laser treatment. Journal of cataract and re-fractive surgery 2009;35:240-7.

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1234. Donnenfeld eD, O’Brien TP, Solomon R,

Perry HD, Speaker MG, Wittpenn J. Infec-tious keratitis after photorefractive kerate-ctomy. Ophthalmology 2003;110:743-7.

235. Teal P, Breslin C, Arshinoff S, edmison D. Corneal subepithelial infiltrates following

excimer laser photorefractive keratectomy. Journal of cataract and refractive surgery 1995;21:516-8.

236. Rosen eS. Risk management in refractive lens exchange. Journal of cataract and re-fractive surgery 2008;34:1613-4.

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ADVANCeD PeRSONALIZeD NOMOGRAM FOR MYOPIC LASeR SURGeRY: FIRST 100 eYeS

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APT NOMOGRAM FOR MYOPIC LASIK AND LASeK

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purpose: To report the results in the first 100 eyes treated for myopia using a new advanced nomogram.

setting: Private refractive surgery clinic.

methods: This prospective interventional case series comprised 58 patients (100 eyes) consecutively treated for myopia with laser in situ keratomileusis (LASIK) or laser-assisted subepithelial keratectomy (LASeK) performed by the same surgeon. All treatments used a new nomogram for the Zyoptix 217 Z100 excimer laser. Postoperative mean sphere, cylinder, and spherical equivalent (Se) refraction were evaluated 3 months postoperatively. Safety, efficacy, and predictability were also evaluated.

results: In the LASIK group (34 eyes), the mean postoperative sphere was +0.18 diopters (D) + 0.47 (SD), the mean postoperative cylinder was -0.10 + 0.23 D, and the mean postoperative Se was +0.04 + 0.36 D. In the LASeK group (64 eyes), the respective means were +0.10 + 0.22 D, -0.05 + 0.13 D, and +0.03 + 0.16 D. Hyperopic overcorrection (> +1.00 D) occurred in 4.1% of patients. Ninety-five percent of eyes in the LASIK group and 97% of eyes in the LASIK group had an uncorrected visual acuity of 1.0 (20/20) or better. Patient satisfaction was slightly higher than that of other laser refractive surgery patients at the clinic.

conclusions: The use of the advanced nomogram increased treatment accuracy in terms of UCVA and postoperative mean refraction and reduced the rate of hyperopic overcorrection over that in earlier studies. The need for enhancement procedures was reduced, and patient satisfaction was high.

ruth lapid-gortzak, md, Jan Willem van der linden, bopt, ivanka J.e. van der meulen, md, carla p. nieuwendaal, md

Private practice (Lapid-Gortzak, van der Linden), Driebergen, and the Department of Ophthalmology (Lapid-Gortzak, van der Meulen, Nieuwendaal), Academic Medical Centre, University of Amsterdam,The Netherlands.

Journal of Cataract Refractive Surgery 2008; 34:1881–1885; 2008 ASCRS and ESCRS

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Customized laser treatment for myopia is an accepted method for treatment of refractive errors. Customized treatments correct the spherical and cylindrical refractive errors as well as higher-order aberrations (HOAs).1–5

even though the outcomes with wavefront technology are good, some treatments result in overcorrection or undercorrection. Analysis of results shows that hyperopic overcorrections occur in approximately 1 in 4 patients; 8% of these eyes require retreatment.5

In the treatment of the spherocylinder, the nomograms used incorporate an adjustment in which the spherical component is routinely decreased in the treatment to offset changes the cylindrical treatment might have on the sphere. This is called the coupling effect.6

In wavefront ablations, some hyperopic overcorrections are induced from the effect of the treatment of preoperative HOAs on postoperative lower-order aberrations (LOAs) (sphere and cylinder) that were not compensated for in the nomogram.5,7 The Advanced Personalized Technology (APT) nomogram, or Rochester nomogram, takes into account the effect the treatment of the preoperative HOAs has on sphere or cylinder and thus induces less postoperative hyperopia. This could be viewed as a type of coupling effect between the preoperative HOA and the postoperative LOA (ie, the sphere and cylinder).5,7 The nomogram also incorporates the preoperative manifest refraction and J0/J45 astigmatic terms to improve accuracy.

The Rochester nomogram was developed by Subbaram and MacRae.5 In other wavefront platforms, the correlation between the effects of treating the preoperative HOA and the resulting postoperative hyperopic overcorrections have also been noted.8–10 Durrie et al.8 and Kermani et al.9 describe similar adjustments to their nomograms that reduced the rate of postoperative hyperopic overcorrections.

We report our experience with the first 100 eyes treated with the APT nomogram for myopia at our refractive center.

patients and methods

The first 100 consecutive eyes treated for myopia with the APT nomogram were analyzed. All treatments took place at the beginning of 2007.

preoperative patient examinationsAll patients had a slitlamp biomicroscopic examination, automated keratometry, manifest refraction, tonometry, corneal topography and pachymetry (Orbscan IIz topographer, Bausch & Lomb), wavefront measurement and pupillometry (Zywave version 5.2, Bausch & Lomb), and dilated fundus examination.

Visual acuity was tested in a high-contrast condensed 3 m lane with early Treatment of Diabetic Retinopathy Study (eTDRS) charts and recorded in metric standard. Patients were tested without contact lenses and were instructed to stop wearing the contact lenses 2 weeks before the examination. All patients received verbal and written information and signed informed consent forms.

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Ultrasonic pachymetry was performed when indicated (corneas < 470 mm on Orbscan). Patients who were not good candidates for laser in situ keratomileusis (LASIK) or laser-assisted subepithelial keratectomy (LASeK) were excluded from treatment according to the guidelines set by the consensus of the Netherlands Society for Refractive Surgery.

Wavefront examinationFive automated Zywave aberrometer measurements were performed, and the best one was chosen. Undilated and dilated (tropicamide 0.5%) wavefront examinations were performed. The pupils of the undilated wavefront examinations were matched for the iris-registration and eye-trackers settings. The dilated examinations were chosen for the wavefront treatment parameters.

patient satisfactionPatients were asked to complete a satisfaction questionnaire on a voluntary basis. The questionnaire was part of the clinic’s quality-control system.

On the questionnaire, patients were asked to grade their satisfaction with their visual outcomes on a scale from 0 (bad) to 10 (excellent). The results were compared with those of other patients who had laser surgery during the same period but with a different nomogram. Because the questionnaire was voluntary and was not administered in a randomized masked fashion, the data were not statistically analyzed.

surgical techniqueAll LASeK and LASIK procedures were performed by the same surgeon (R.L.G.). Room temperature was between 19o C and 21o C and humidity, between 28% and 34%. The same excimer laser (Zyoptix 217 Z100, Bausch & Lomb) with Keracor 3.21 Dataware, treatment calculator 2.38, and Zywave software version 5.2 was used.

In all LASIK cases, a Zyoptix XP 120 microkeratome (Bausch & Lomb) was used. Laser-assisted subepithelial keratectomy was performed with 20% alcohol solution for 30 seconds. The epithelium was returned to the stromal bed in all cases.

For ablation profiles deeper than 100 mm, mitomycin-C 0.02% was applied for 12 seconds and then irrigated with 30 cc of a balanced salt solution.

statistical analysisStatistical analysis was performed using the statistical functions of excel Windows 2000 (Microsoft Corp.)

results

preoperative dataOne hundred eyes of 58 patients were treated. There were 36 eyes (19 patients) in the LASIK group and 64 eyes (39 patients) in the LASeK group. Fifty percent in the LASIK group and 52% in the LASeK group were women.

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In the LASIK group, 25% of eyes had a spherical equivalent (Se) refractive error up to -2.0 diopters (D), 41% between -2.0 D and -4.0 D, 41% between -4.0 D and -6.0 D, and 3% greater than -6.0 D. In the LASeK group, 9% of eyes had an Se refractive error up to -2.0 D, 48% between -2.0 D and -4.0 D, 30% between -4.0 D and -6.0 D, and 13% greater than -6.0 D.

Table 1 shows the preoperative mean sphere, cylinder, and Se refraction in the LASIK and LASeK groups. No eye had a best corrected visual acuity (BCVA) of 1.6 preoperatively. eleven eyes had a BCVA of 1.25 (20/16), and 82 had a BCVA of 1.0 (20/20). One eye had a BCVA of 0.63 (20/30), 2 eyes of 0.8 (20/25) and 4 eyes of 0.9 (20/22).

postoperative data at 3 monthsefficacy Table 2 shows the major outcome indices. The efficacy index was 1.13 in the LASIK group and 1.26 in the LASeK group.

Ninety-five percent of eyes in the LASIK group and 97% of eyes in the LASIK group had an uncorrected visual acuity (UCVA) of 1.0 (20/20) or better. Figure 1 shows the postoperative UCVA compared with the preoperative BCVA.

Predictability Figure 2 shows the percentage of eyes within +1.00 D, +0.50 D, and +0.25 D of the target Se refraction at 3 months. Postoperatively, 90.0% of eyes in the LASIK group and 93.7% of eyes in the LASeK group were within +0.25 D of the target refraction.

table 1: Pre-operative and Post-operative refraction.

refraction (d) lasik group lasek group

preoperative mean + sd range mean + sd range

Sphere -2.50 + 1.40 +0.25 to -5.75 -3.21 + 1.6 +0.25 to -7.75

Cylinder -1.06 + 0.82 0.00 to -2.75 -1.11 + 0.84 0.00 to -3.25

Se -3.03 + 1.47 0.00 to -6.12 -3.77 + 1.56 -1.12 to -7.87

postoperative

Sphere +0.18 + 0.47 -0.50 to +1.50 +0.10 + 0.22 -0.50 to +1.00

Cylinder -0.10 + 0.23 0.00 to -0.75 -0.05 + 0.13 0.00 to -0.75

Se +0.04 + 0.36 -0.87 to +1.50 +0.03 + 0.16 -0.12 to +1.00

LASIK = laser in situ keratomileusis; LASeK = laser-assisted subepithelial keratectomy; Se = spherical equivalent

table 2: Major outcome indices

parameter

group

lasik lasek

Safety 1.19 1.27

efficacy 1.13 1.26

UCVA O1.0 (20/20) (%) 95.0 97.0

Within + 1.00 D (%) 97.0 98.4

Within + 0.50 D (%) 93.0 95.2

Within + 0.25 D (%) 90.9 93.7

(LASeK = laser-assisted subepithelial keratectomy; LASIK = laser in situ Keratomileusis)

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figure 1. Postoperative UCVA compared with preoperative BCVA (BCVA = best corrected visual acuity; LASEK = laser-assisted subepithelial keratectomy; LASIK = laser in situ keratomileusis; UCVA = uncorrected visual acuity; VA = visual acuity).

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Figure 1. Postoperative UCVA compared with preoperative BCVA (BCVA = best corrected visual acuity; LASEK = laser-assisted subepithelial keratectomy; LASIK = laser in situ keratomileusis; UCVA = uncorrected visual acuity; VA = visual acuity). Safety The safety index was 1.19 in the LASIK group and 1.27 in the LASEK group. Figure 3 shows the lines of UCVA gained or lost compared with the preoperative BCVA. In some cases, lost lines were regained after enhancement procedures.

Figure 2. Predictability of LASIK and LASIK for +1.0 D, +0.5 D, and +0.25 D (LASEK = laser-assisted subepithelial keratectomy; LASIK = laser in situ keratomileusis).


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figure 2. Predictability of LASIK and LASIK for +1.0 D, +0.5 D, and +0.25 D (LASEK = laser-assisted subepithelial keratectomy; LASIK = laser in situ keratomileusis).


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Figure 3. Safety in terms of lines lost and gained in percentages (LASEK = laser-assisted subepithelial keratectomy; LASIK = laser in situ keratomileusis).

Four eyes had a significant hyperopic overcorrection (>1.0 D); 2 eyes (1 patient) were in the LASIK group and 2 (1 patient), in the LASEK group. The rate of hyperopic correction was 4.1%, 5.8% in the LASIK group and 3.2% in LASEK group (Table 3). Mean + SD Percentage

Study Sphere (D) SE (D) % > 20/20 Hyperopic Overcorrection

Rochester (APT)5

+0.04 + 0.33 -0.11 + 0.34 93.1

2.8

FDA trial5 +0.31 + 0.53 +0.15 + 0.53 89.3 22.3

Current

LASIK +0.18 + 0.47 +0.04 + 0.36 95.0 5.8* LASEK +0.10 + 0.22 +0.03 + 0.16 97.0 3.2*

FDA = U.S. Food and Drug Administration; LASIK = laser in situ keratomileusis; LASEK = laser-assisted subepithelial keratectomy; SE = spherical equivalent *Overall rate, 4.1% Table 3: Comparison of post-operative mean refractive data, efficacy, and hyperopic overcorrection rates between studies. Follow-up Compliance Ninety-seven percent of eyes were seen at the 3-month follow-up. Two eyes with LASIK (1 patient) and 1 eye with LASEK were lost to follow-up. When contacted by telephone, the patients reported that they were satisfied and doing well but declined a follow-up visit. Patient Satisfaction Twenty-five (43%) of 58 patients completed the voluntary questionnaire. The mean grade was 9.52. Fifty other patients who had laser treatment during the same period with other nomograms filled out the questionnaire; the mean grade was 9.01.


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Figure 3. Safety in terms of lines lost and gained in percentages (LASEK = laser-assisted subepithelial keratectomy; LASIK = laser in situ keratomileusis).

Four eyes had a significant hyperopic overcorrection (>1.0 D); 2 eyes (1 patient) were in the LASIK group and 2 (1 patient), in the LASEK group. The rate of hyperopic correction was 4.1%, 5.8% in the LASIK group and 3.2% in LASEK group (Table 3). Mean + SD Percentage

Study Sphere (D) SE (D) % > 20/20 Hyperopic Overcorrection

Rochester (APT)5

+0.04 + 0.33 -0.11 + 0.34 93.1

2.8

FDA trial5 +0.31 + 0.53 +0.15 + 0.53 89.3 22.3

Current

LASIK +0.18 + 0.47 +0.04 + 0.36 95.0 5.8* LASEK +0.10 + 0.22 +0.03 + 0.16 97.0 3.2*

FDA = U.S. Food and Drug Administration; LASIK = laser in situ keratomileusis; LASEK = laser-assisted subepithelial keratectomy; SE = spherical equivalent *Overall rate, 4.1% Table 3: Comparison of post-operative mean refractive data, efficacy, and hyperopic overcorrection rates between studies. Follow-up Compliance Ninety-seven percent of eyes were seen at the 3-month follow-up. Two eyes with LASIK (1 patient) and 1 eye with LASEK were lost to follow-up. When contacted by telephone, the patients reported that they were satisfied and doing well but declined a follow-up visit. Patient Satisfaction Twenty-five (43%) of 58 patients completed the voluntary questionnaire. The mean grade was 9.52. Fifty other patients who had laser treatment during the same period with other nomograms filled out the questionnaire; the mean grade was 9.01.

figure 3. Safety in terms of lines lost and gained in percentages (LASEK = laser-assisted subepithelial keratectomy; LASIK = laser in situ keratomileusis).

safety The safety index was 1.19 in the LASIK group and 1.27 in the LASeK group.

Figure 3 shows the lines of UCVA gained or lost compared with the preoperative BCVA. In some cases, lost lines were regained after enhancement procedures.

Four eyes had a significant hyperopic overcorrection (>1.0 D); 2 eyes (1 patient) were in the LASIK group and 2 (1 patient), in the LASeK group. The rate of hyperopic correction was 4.1%, 5.8% in the LASIK group and 3.2% in LASeK group (Table 3).


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follow-up complianceNinety-seven percent of eyes were seen at the 3-month follow-up. Two eyes with LASIK (1 patient) and 1 eye with LASeK were lost to follow-up. When contacted by telephone, the patients reported that they were satisfied and doing well but declined a follow-up visit.

patient satisfactionTwenty-five (43%) of 58 patients completed the voluntary questionnaire. The mean grade was 9.52. Fifty other patients who had laser treatment during the same period with other nomograms filled out the questionnaire; the mean grade was 9.01.

mitomycin cMitomycin-C was applied in 2 eyes of 2 patients. One of the eyes was lost to follow-up; in the other eye, the postoperative UCVA was 1.25 and no haze was seen.

discussion

In our study, the ATP nomogram, also known as the Rochester nomogram,5 provided accurate refractive outcomes. Ninety-five percent of LASIK treated eyes and 97% of LASeK-treated eyes achieved a postoperative UCVA of 1.0 (20/20). In a study of the Rochester nomogram by Subbaram and MacRae,5 91.5% of eyes were within +0.50 D of the target refraction and 100% were within +1.00 D. In the Zyoptix U.S. Food and Drug Administration (FDA) trial,5 72.6% of eyes were within +0.50 D and 90.2% were within +1.00 D. In a study by Kohnen et al.1 of the Zyoptix 3.1 nomogram, 77% of eyes were within +0.50 D of target refraction at 1 year and 95% were within +1.00 D.

In our study, 93.0% of eyes in the LASIK group were within +0.50 D of the target refraction and 97.0% were within +1.00 D. In the LASeK group, 95.2% were within +0.50 D and 98.4% were within +1.00 D. These outcomes reflect the high predictive accuracy of the advanced nomogram.

table 3: Comparison of post-operative mean refractive data, efficacy, and hyperopic overcorrection rates between studies.

study

mean + sd percentage

sphere (d) se (d) % > 20/20 hyperopic overcorrection

Rochester (APT)5 +0.04 + 0.33 -0.11 + 0.34 93.1 2.8

FDA trial5 +0.31 + 0.53 +0.15 + 0.53 89.3 22.3

current

LASIK +0.18 + 0.47 +0.04 + 0.36 95.0 5.8*

LASeK +0.10 + 0.22 +0.03 + 0.16 97.0 3.2*

FDA = U.S. Food and Drug Administration; LASIK = laser in situ keratomileusis; LASeK = laser-assisted subepithelial keratectomy; Se = spherical equivalent *Overall rate, 4.1%

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The FDA Zyoptix study used a wavefront nomogram without the spherical correction for the treatment of the HOAs. The study found consecutive hyperopia in 22.3% of cases, one third of which required an enhancement (Table 3).5

Subbaram and MacRae5 report a hyperopic overcorrection (>1.0 D) in 2.8% of patients treated with the advanced nomogram. Our study confirms this low rate of hyperopic overcorrection. We had a slightly higher rate (4.1%) of overcorrection. This may be a coincidence or because our study included 100 eyes, while Subbaram and MacRae’s study comprised 175 eyes. It may also be because we had not inserted our own offset factor into the nomogram. Our results were slightly hyperopic in the first 100 eyes. A simple sphere adjustment would probably alleviate this.

The Se postoperative outcomes of +0.04 D and +0.03 D are very close to plano. The standard deviations of these results, of 0.36 D and 0.16 D, respectively, are close to and below the repeatability of the manifest refraction.11–13 This means that the advanced personalized nomogram is highly accurate. In clinical practice, this was matched by patient satisfaction.

The differences in outcomes and results between the LASIK group and the LASeK group were small. Discussion of the preferential treatment mode of LASIK versus LASeK is beyond the scope of this paper; thus, these data were not explored or discussed.

The greater accuracy of the nomogram decreased the retreatment rate. The lower retreatment rate increased patient safety and satisfaction. The good efficacy and safety rates in our study reflect the improved postoperative UCVA in our patients. Similar indices were reported by Durrie et al.8 on the Alcon platform.

Both patients with hyperopic overcorrection were men in their mid-40s. No preoperative risk factor for hyperopic overcorrection could be identified. Further study is needed to determine whether specific clinical characteristics can predict which groups of patients are at risk for hyperopic correction even when the adjusted nomogram is used.

We used the wavefront measurements with the eye pharmacologically dilated for matching with the advanced nomogram. Subbaram and MacRae5 report that pharmacological pupil dilation may cause a pupil shift, which may cause changes on the wavefront that can be clinically significant. Although the wavefront changes significantly as the pupil dilates and there is an increase in HOAs with wider pupils, the advanced personalized nomogram has a feature in which a measured pupil with a corresponding wavefront can be mathematically extrapolated for a pupil with a 10% larger diameter.5,7,14 This could make it possible to perform wavefront examinations with the pupil undilated, without the need for examination with the pupil dilated. In our clinic, the protocol requires that we perform both undilated and dilated wavefront examinations; we use the pharmacologically dilated wavefront measurements in the actual treatment. The Zywave prediction of phoropter refraction is usually more myopic than the subjective refraction.15 This effect of instrument myopia is alleviated with cycloplegia. That we use dilated wavefront data with minor cycloplegia may, in theory, affect the hyperopic overcorrection and account for the low rate of hyperopic

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overcorrection in our patients. This requires further study. Long-term stability and the possibility for refinement of the advanced nomogram must also be studied.

In conclusion, we found the ATP to be a highly accurate nomogram for treating myopia, leading to Se refractions that were close to plano as well as high patient satisfaction.

references

1. Kohnen T, Bühren J, Kühne C, Mirshahi A. Wavefront-guided LASIK with the Zyoptix 3.1 system for the correction of myopia and compound myopic astigmatism with 1-year follow-up; clinical outcome and change in higher order aberrations. Oph-thalmology 2004; 111:2175–2185

2. Lawless MA, Potvin RJ. Fulfilling the prom-ise of laser refractive surgery. J Refract Surg 2006; 22:S965–S968

3. Netto MV, Dupps W Jr, Wilson Se. Wave-front-guided ablation: evidence for effica-cy compared to traditional ablation. AmJ Ophthalmol2006; 141:360–368

4. Randleman JB, Loft eS, Banning CS, Lynn MJ, Stulting RD. Outcomes of wavefront-optimized surface ablation. Ophthalmol-ogy 2007; 114:983–988

5. Subbaram MV, MacRae SM. Customized LASIK treatment for myopia based on pr-eoperative manifest refraction and higher order aberrometry: the Rochester nomo-gram. J Refract Surg 2007; 23:435–441

6. Vinciguerra P. Cross-cylinder ablation for the correction of myopic or hyperopic astigmatism. In: Gimbel HV, Anderson Penno eA, eds, Refractive Surgery; A Man-ual of Principles and Practice. Thorofare, NJ, Slack, 2000; 105–113

7. Subbaram MV, MacRae SM. Does dilated wavefront aberration measurement pro-vide better postoperative outcome af-ter custom LASIK? Ophthalmology 2006; 113:1813–1817

8. Durrie DS, Stahl Je, Schwendeman F. Al-con LADARWave CustomCornea retreat-ments. J Refract Surg 2005; 21:S804–S807

9. Kermani O, Schmiedt K, Oberheide U, Gerten G. Topographic and wavefront-guided customized ablations with the NIDeK eC5000-XII in LASIK for myopia. J Refract Surg 2006; 22:754–763

10. Schwartz GS, Park DH, Lane SS. Cus-tomCornea wavefront retreatment af-ter conventional laser in situ keratomi-leusis. J Cataract Refract Surg 2005; 31: 1502–1505

11. Blackhurst DW, Maguire MG. Reproduci-bility of refraction and visual acuity meas-urement under a standard protocol; the Macular Photocoagulation Study Group. Retina 1989; 9:163–169

12. Bullimore MA, Fusaro Re, Adams CW. The repeatability of automated and clini-cian refraction. Optom Vis Sci 1998; 75: 617–622

13. Nizam A, Warring GO III, Lynn MJ, Ward MA, Asbell PA, Balyeat HD, Cohen e, Culbertson W, Doughman DJ, Fecko P, McDonald M, Smith Re. Stability of re-fraction and visual acuity during 5 years in eyes with simple myopia; the PeRK Study Group. Refract Corneal Surg 1992; 8:439–447

14. Wilson MA, Campbell MCW, Simonet P. Change of pupil centration with change of illumination and pupil size; the Julius F. Neumueller Award in Optics. Optom Vis Sci 1992;69:129–136

15. Hament WJ, Nabar VA, Nuijts RMMA. Re-peatability and validity of Zywave aber-rometer measurements. J Cataract Refract Surg 2002; 28:2135–2141

LASIK AND LASeK AFTeR ReFRACTIVe LeNS eXCHANGe WITH DIFFRACTIVe MULTIFOCAL

IOL IMPLANTATION

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BIOPTICS WITH MULTIFOCAL IOL's

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abstract

purpose: To evaluate the efficiency and safety of excimer laser procedures for residual refractive errors after refractive lens exchange (RLe) with a diffractive multifocal IOL (Restor™) at 3 and 6 months.

setting: Private refractive Surgery Clinic, Retina, Driebergen, the Netherlands.

methods: Forty seven eyes (25 patients) had either LASIK or LASeK for residual ametropia after RLe. LASeK was performed with 30 sec 20% alcohol, LASIK with the XP microkeratome. The Technolas excimer laser was used in all eyes. Outcome measures were the post-operative spherical equivalent (Se), sphere and cylindrical refraction for distance, uncorrected distance acuity (UDVA), corrected distance acuity (CVA), uncorrected near visual acuity (UNVA), patient satisfaction based on questionnaires, complication rate, and retreatment percentage.

results: In LASIK mean pre-operative Se refraction was +0.50D + 0.72 D (range -1.88 to +1.25). Mean post-operative Se was +0.29 +0.34 D (range -0.25 to +1.00). Visual acuity improved from a mean UDVA of 0.63 to 1.08 and 1.13 at 3 and 6 months, respectively. UNVA improved from 0.96 to 0.99. In LASeK mean pre-operative Se was +0.34 D + 0.73 D (range -0.75 to +1.5D). Postoperatively mean Se was +0.21 D + 0.13D. UDVA improved from 0.58 to 0.99 and 1.13 at 3 and 6 months, respectively. UNVA improved from 0.96 to 0.99. The change in UDVA and CVA was statistically significant (p<0.001 paired t-test). Patient satisfaction was graded 8.6 on a scale of 10.

conclusions: LASIK and LASeK for small residual errors is efficacious and safe. It provides the patients the uncorrected far and near vision that was intended with the multifocal IOL implantation.

keyWords: LASIK, LASeK, excimer laser, bioptics, multifocal IOL

ruth lapid-gortzak md 1,2 , Jan Willem van der linden boptom 1, raphael saidof ma, ivanka Je van der meulen md1,2, carla p nieuwendaal md 2, and maarten p mourits md phd 2

1Retina Total Eye Care, Driebergen, the Netherlands; 2Dept. of Ophthalmology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.

Submitted for publication

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introduction

Refractive lens exchange (RLe) is a procedure in which the crystalline lens is removed and exchanged for an intra-ocular lens. The indications for these procedures are still developing. The main finding in the patients seeking this procedure is the fact that they are presbyopic and need different spectacle correction for far and near vision, and are motivated to do a procedure which may enhance their spectacle freedom. A residual refractive error is a reason for reduced patient satisfaction.1 Postoperative halos and visual disturbances are other reasons for dissatisfaction.2

excimer laser has been a safe and efficient way to treat myopia and some forms of hyperopia and astigmatism with success.

The combination of the use of RLe and a corneal laser procedure is known as bioptics.3-4 The indication for bioptics is the existence of a refractive error after an intra-ocular lens procedure. There are 2 reasons for residual ametropia. Preexisting corneal astigmatism that cannot be corrected by this specific spherical intra-ocular lens, and a residual refractive error as a result of surgically induced astigmatism or IOL decentration during surgery or wound healing.

Safety and efficiency of corneal laser refractive surgery after pseudophakia have been described .5-7 PRK on multifocal pseudophakic eyes has been described by Lescicotti in 2004.2 Zaldivar treated a mean refractive error of -2.61 D.4 The range of residual refractive errors in other studies ranged from -2.19 D to -3.76 D with astigmatism up to 6 D treated. 8-12 The post-operative LASIK and PRK spherical equivalent refraction ranged between -0.88 D to +0.09D. The range of indications for corneal laser refractive procedures in (multifocal) pseudophakia has not yet been described in guidelines. One of the questions is – at what refractive error, and what level of uncorrected distance acuity should such a procedure be performed?

methods

In a prospective consecutive case-series, 26 patients (45 eyes) with a residual refractive error after refractive lens exchange with the Restor +4, were studied. The Tenets of the Declaration of Helsinki were adhered to.

Both the RLe and the corneal laser procedures were done by a single surgeon (RLG). All RLe procedures were done between November 2007 and April 2009. RLe was done after oral and written informed consent of the patient. The IOL choice was based on the IOLmaster 5.0 (Zeiss, Germany) with emmetropia as the target. RLe was performed with the Ozil, Infiniti (Alcon, Forth Worth, USA), with a 2.75 near clear 12 o’clock incision. Curvilinear capsulorrhexis was done in all cases, with the optic of the intra-ocular lens (IOL) being covered by the rhexis edge. A Restor +4D (Alcon, Fort Worth, USA) was implanted in all these cases. Vigorous anterior and posterior capsular polishing was performed.

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Indication for LASIK and LASeK after the RLe was dissatisfaction of the patient with the uncorrected distance vision, which could be corrected with a spherocylindrical spectacle correction. The secondary indications were either a pre-operative cylinder that could not be corrected with the incision, a residual ametropia that improved with corrective lenses (a planned enhancement), or a residual refractive error that improved with refraction (an enhancement because of a surprise in refractive outcome after RLe).

The patients had to have improved visual acuity after manifest refraction. Other causes of visual loss were considered to be exclusion criteria for laser enhancement after RLe.

Informed consent for the study was obtained from all the participants. Pre-operatively patients underwent a complete ophthalmic examination, including

uncorrected and corrected distance visual acuity (UCDA, BCDA), near visual acuity (NVA), autorefraction and manifest refraction, slitlamp examination, tearfilm assessment by fluorescein staining, tear breakup time measurement, and Schirmer’s testing with anesthetic eyedrops, tonometry, orbscan topography, orbscan pachymetry and on indication sonogage pachymetry, dilated fundoscopy and biomicroscopy, assessment of IOL position, and posterior capsular clarity. Baseline retreatment refraction was done at least 12 weeks post RLe. Refraction had to be stable, and without contact lenses to prevent treating warpage effects.

LASIK was performed with the Technolas Z217 and the 120 XP microkeratome (Technolas, Munich, Germany). LASeK was done with 20% alcohol for 30 seconds, and rinse with BSS. Standard ablations were done with the Planoscan Nomogram (Technolas, Munich, Germany) Manifest refraction was used for the treatment planning.

LASIK or LASeK was performed according to the Guidelines of the Netherlands Society of Refractive Surgeons (2006 edition), and according to patients’ preference. There was no minimal stated refraction to be eligible for the procedure.

Outcome measurements are distance and near visual acuity, uncorrected and corrected, efficacy and safety indices, complications, patient satisfaction, retreatment rates, mean Se refraction, mean sphere and cylinder refraction, pre and post laser enhancement procedure, and the patient satisfaction as recorded (scale 1 bad 10 best) on the questionnaire we routinely use in our clinic.

results

demographic dataWe describe the results of 45 eyes of 26 patients which had consecutive enhancement procedures done for residual refractive errors after RLe.

The mean age was 58.89 years, with a range of 51.5 to 66.17 years. Of the patients 80.7% were males.

In 27 eyes LASeK was done, and in 18 eyes LASIK was performed. The initial refraction before RLe was hyperopic in 22 eyes, and myopic in 23 eyes.

In the LASIK group a planned bioptics procedure was done in 6 of the 18 eyes. In the

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other 12 eyes the indication was an unplanned residual error. In LASeK 19 of 27 eyes a planned bioptics procedure was done.

pre-operative dataIn the LASIK group there were 18 eyes. The mean age was 57.1 years (range 51.5-63 years). The pre-operative spherical equivalent refraction was 0.50D + 0.72 D (range 0

table 1: pre-operative and post-operative refractive and visual acuity results in LASIK.

parameter pre-operative post-operative at 3 months 6 months

refraction (d)

Se 0.50 + 0.72 (0 to +1.25)

0.29 + 0.34 (-0.25 to +1.0)

0.10 + 0.23 (-0.25 to +0.62)

Sphere 1.21 + 0.62 (-0.75 to 1.5)

0.43 + 0.33 ( plano to 1.25)

0.23 + 0.75 (plano to +0.75)

Cylinder -1.01 + 0.62 (plano to -2.25)

-0.30 + 0.39 ( plano to -1.00)

-0.25 + 0.39 (plano to -1.00)

Visual acuity

UDVA 0.63 + 0.2 (0.32-0.9)

1.08 + 0.18 (0.8-1.25)

1.13 + 0.16 (0.8-1.25)

CDVA 1.1 + 0.16 (0.9-1.5)

1.175 + 0.22 (0.8-1.6)

1.21 + 0.20 (0.9-1.6)

UNVA 0.96 + 0.09 (0.8-1.0)

0.99 + 0.05 (0.8-1.0)

0.99 + 0.05 (0.8-1.0)

All values are written as the mean with standard deviation, with the range between parenthesis.

table 2: pre-operative and post-operative refractive an visual acuity results in LASEK.

parameter pre-operative 3m post-operative 6 months

refraction

Se 0.34 D + 0.73 D ( -0.75 to +1.5)

plano + 0.5D (-0.625 to +0.625D)

-0.06 + 0.22 (-0.62 to +0.62)

Sphere 1.09 + 0.2 (-0.25 to 2.5)

+0.17D + 0.50 D (-0.25 to +1.25 D)

0.04 + 0.23 (-0.25 to +0.75)

Cylinder -1.44 + 0.59 (-0.5 to -2.75 D

-0.32 D + 0.42 D (plano to -1.25 D)

-0.20 + 0.28 (plano to -0.75)

Visual acuity

UDVA 0.58 + 0.19 (0.32-0.8)

0.99 + 0.26 (0.32-1.35)

1.13 +0.21 (0.8-1.6)

CDVA 1.05 + 0.17 (0.7-1.25)

1.11 + 0.16 (0.63-1.35)

1.18+ 0.20 (0.8-1.6)

UNVA 0.96 + 0.09 (0.8-1.0)

0.99 + 0.05 (0.8-1.0)

0.97 + 0.08 (0.8-1.0)

All values are written as the mean with standard deviation, with the range between parenthesis.

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to +1.25). The mean pre-operative sphere was +1.21 D + 0.62 D (range from +0.75 to +1.50). The pre-operative cylinder was -1.01 D + 0.62 D (range 0 to -2.25 D). The mean pre-operative uncorrected distance visual acuity (UDVA) was 0.63 + 0.2 (range 0.32 to 0.9). The pre-operative corrected distance visual acuity (CDVA) was 1.1 + 0.16 (range 0.9 to 1.5). The pre-operative uncorrected near visual acuity (UNVA) was 0.96 + 0.09 (0.8-1.0). The mean time between the RLe and the LASIK was 191 days + 62 (range 125 days to 362 days).

In the LASeK group there were 27 eyes. The mean age was 60.1 years (range 54.5-66.2 years). The mean pre-operative spherical equivalent refraction was +0.34 D + 0.73 D (range -0.75 to +1.5). The pre-operative mean sphere was 1.09 + 0.2 (-0.25 to 2.5). The pre-operative cylinder was -1.44 + 0.59 (range -0.5 to -2.75 D). The pre-operative UDVA was 0.58 + 0.19 (range 0.32-0.8), and the mean CDVA was 1.05

figure 1: Attempted versus achieved sphere correction in LASIK and LASEK bioptics. The diagonal lines represent + 0.5 D of the y=x.

3 LASIK and LASEK after RLE with MFIOL implantation

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Table 1: pre-operative and post-operative refractive and visual acuity results in LASIK. All values are written as the mean with standard deviation, with the range between parenthesis.

Figure 1: Attempted versus achieved sphere correction in LASIK and LASEK bioptics. The diagonal lines represent + 0.5 D of the y=x.

0

0.5

1

1.5

2

2.5

3

0 0.5 1 1.5 2 2.5 3

Attempted correction

Achi

eved

cor

rect

ion

lasek 3 monthslasik 3 months

Table 1: Parameter Pre-operative Post-operative at 3

months 6 months

Refraction (D) SE 0.50 + 0.72 (0 to +1.25) 0.29 + 0.34 (-0.25 to

+1.0) 0.10 + 0.23 (-0.25 to +0.62)

Sphere 1.21 + 0.62 (-0.75 to 1.5)

0.43 + 0.33 ( plano to 1.25)

0.23 + 0.75 (plano to +0.75)

Cylinder -1.01 + 0.62 (plano to -2.25)

-0.30 + 0.39 ( plano to -1.00)

-0.25 + 0.39 (plano to -1.00)

Visual Acuity UDVA 0.63 + 0.2 (0.32-0.9) 1.08 + 0.18 (0.8-1.25) 1.13 + 0.16 (0.8-

1.25) CDVA 1.1 + 0.16 (0.9-1.5) 1.175 + 0.22 (0.8-1.6) 1.21 + 0.20 (0.9-1.6) UNVA 0.96 + 0.09 (0.8-1.0) 0.99 + 0.05 (0.8-1.0) 0.99 + 0.05 (0.8-1.0)


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Figure 2: Attempted versus achieved cylinder correction in LASIK and LASEK bioptics. The diagonal lines represent + 0.5D from the y=x.

Figure 3: Lines lost and gained in LASIK and LASEK bioptics at 3 and 6 months. Most losses of lines were due to refractive error.

0

0.5

1

1.5

0.00 0.50 1.00 1.50


Achi

eved

cor

rect

ion

lasik cyl correctionlasek cyl correction

Lines gained and lost at 3 & 6 m

0%

20%

40%

60%

80%

100%

<-2 -1 0 1 >+2

lines

%

lasik 3mlasik 6mlasek 3mlasek 6 m

figure 2: Attempted versus achieved cylinder correction in LASIK and LASEK bioptics. The diagonal lines represent + 0.5D from the y=x.

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Figure 2: Attempted versus achieved cylinder correction in LASIK and LASEK bioptics. The diagonal lines represent + 0.5D from the y=x.

Figure 3: Lines lost and gained in LASIK and LASEK bioptics at 3 and 6 months. Most losses of lines were due to refractive error.

0

0.5

1

1.5

0.00 0.50 1.00 1.50


Achi

eved

cor

rect

ion

lasik cyl correctionlasek cyl correction

Lines gained and lost at 3 & 6 m

0%

20%

40%

60%

80%

100%

<-2 -1 0 1 >+2

lines

%

lasik 3mlasik 6mlasek 3mlasek 6 m

figure 3: Lines lost and gained in LASIK and LASEK bioptics at 3 and 6 months. Most losses of lines were due to refractive error. 3 LASIK and LASEK after RLE with MFIOL implantation

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Figure 4: Predictability of the LASIK and LASEK bioptics treatments.

Figure 5: Visual acuity in Snellen lines pre-operatively versus post-operatively in LASIK bioptics. The blue hues are pre-operative visual acuity, while the red hues are the post-operative visual acuities. We see an improvement in both corrected and uncorrected visual acuities for distance and near vision.

0%

20%

40%

60%

80%

100%

<0.5 0.63 0.8 1 1.25 1.6

pre-opUDVApre-op CDVApre-op UNVA3 m UDVA3m CDVA3m UNVA

h

Accuracy of target spherical equivalent refraction

0%

20%

40%

60%

80%

100%

120%

within 0.25 D within 0.5 D within 1.0 D

lasik 3 m lasik 6 m lasek 3 m lasek 6 m


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Figure 4: Predictability of the LASIK and LASEK bioptics treatments.

Figure 5: Visual acuity in Snellen lines pre-operatively versus post-operatively in LASIK bioptics. The blue hues are pre-operative visual acuity, while the red hues are the post-operative visual acuities. We see an improvement in both corrected and uncorrected visual acuities for distance and near vision.

0%

20%

40%

60%

80%

100%

<0.5 0.63 0.8 1 1.25 1.6


h

Accuracy of target spherical equivalent refraction

0%

20%

40%

60%

80%

100%

120%

within 0.25 D within 0.5 D within 1.0 D

lasik 3 m lasik 6 m lasek 3 m lasek 6 m

figure 4: Predictability of the LASIK and LASEK bioptics treatments.

figure 5: Visual acuity in Snellen lines pre-operatively versus post-operatively in LASIK bioptics. The blue hues are pre-operative visual acuity, while the red hues are the post-operative visual acuities. We see an improvement in both corrected and uncorrected visual acuities for distance and near vision.

figure 6: Visual acuity in Snellen lines pre-operatively versus post-operatively in LASEK bioptics. The blue hues are pre-operative visual acuity, while the red hues are the post-operative visual acuities. We see an improvement in both corrected and uncorrected visual acuities for distance and near vision.


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Figure 6: Visual acuity in Snellen lines pre-operatively versus post-operatively in LASEK bioptics. The blue hues are pre-operative visual acuity, while the red hues are the post-operative visual acuities. We see an improvement in both corrected and uncorrected visual acuities for distance and near vision. Discussion: In our study we show that both LASIK and LASEK are effective in treating small residual refractive errors after refractive lens exchange. The difference between both the UCDA and BCDA pre-operatively versus the post-operative UCDA was clinically as well as statistically significant. In some patients (3 eyes) more than 1 procedure was needed to reach emmetropia. No severe adverse events were seen in the study group. A review of the literature shows that multifocal lenses are effective in restoring far and near vision in patients with cataract and also in clear lens extraction13-16. Patient satisfaction depends on how well maximal uncorrected visual acuity was achieved. With the current IOL technology small residual errors are the leading cause of dissatisfaction,1, 17 whereas only a few years ago the main limitation was the photic phenomena caused by the older generation multifocal IOL’s. 15 Motivation is an important factor in satisfaction after multifocal IOL implantation and acceptance of visually disturbing phenomena.14 The only factor that can be improved after implantation is treatment of the residual refractive error. LASIK and LASEK have been shown to be predictable and safe after cataract surgery with monofocal lens implantations. 2-4, 6, 8-11, 18 There are few reports of LASIK and LASEK for residual errors after multifocal IOL implantation and overall the results are good.19-21 Predictability is another issue that plays a role in the decision to treat small residual refractive errors after a multifocal IOL implantation. In our study the results of LASIK and LASEK were clinically and statistically similar. Treatment resulted in a decrease in the refractive error, and an increase in the UCDA. Review of the literature shows the residual refractive error being higher than the refractive error that we decided to treat. In contrast to the study done by Piñero et al22, we did not divide the

0%

20%

40%

60%

80%

100%

<0.5 0.63 0.8 1 1.25 1.6


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+ 0.17 (0.7-1.25). The pre-operative UNVA was 0.96 + 0.23 (0.8-1). The mean time elapsed between RLe and the LASeK was 175 days + 70 days (range 84 days to 364 days).

post operative results in the lasik group at 3 months (18 eyes) The mean UDVA was 1.08, while the mean UNVA was 0.99. The post-operative spherical equivalent was +0.29 D ++ 0.34 D (range -0.25 to +1.0D). The mean post-operative sphere was +0.43 + 0.33 (range plano to +1.25). The mean post-operative cylinder was -0.30 D + 0.39 D (range 0 to -1.00D). Distance efficacy was 0.98, near efficacy was 1.01. Safety was 1.07.

post-operative results in the lasik group at 6 month (14 eyes) The mean UDVA was 1.13 and the UNVA was 0.99. The mean post operative spherical equivalent was +0.10 + 0.0.23 ( range -0.25to +0.62). The mean post-operative sphere was +0.23 + 0.3 ( range plano to +0.75), and the mean post-operative cylinder was -0.25 + 0.39 (range plano to -1.00). Four eyes of 3 patients were lost to follow up.

post-operative results in the lasek group at 3 months (27 eyes) The mean UDVA was 0.99, and the mean UNVA was 0.99. The mean post-operative Se was plano + 0.5D (range -0.625 to +0.625D). The mean post-operative sphere was +0.17D + 0.50 D (range -0.25 to +1.25 D). The mean post-operative cylinder was -0.32 D + 0.42 D (range plano to -1.25 D). efficacy for distance was 0.94 and for near 1.01. Safety was 1.06. In 3 eyes (2 patients) a second lasek procedure was needed. One of these patients had a map dot fingerprint dystrophy, and the other had no complicating factor. In all 3 eyes, VA was satisfactory after the second LASeK procedure. (UDVA 1.25, 1.0, 1.0). The LASeK enhancement rate was 11.1%.

post-operative results in the lasek group at 6 months (24 eyes) The mean UDVA was 1.13 and the mean UNVA was 0.97. The post-operative Se was -0.06 + 0.22 D (range -0.62 to +0.62D). The mean post-operative sphere was +0.04 + 0.23 D (range -0.25 to +0.75 D), and the mean post-operative cylinder was -0.20 D + 0.28 D (range plano to -0.75).

Three eyes of 2 patients were lost to follow up.

complications and patient satisfaction All patients completed a questionnaire following their RLe treatment and after the bioptics enhancement. One patient in each group (3 eyes) said they regretted their decision to have the procedure done, even though their Snellen acuity for far and near was equal to or exceeded the 1.0 (20/20). The mean grade the patients gave their satisfaction with the treatment and outcome on a scale of 1 (extremely bad) to 10 (excellent) was 8.6.

No serious adverse events were seen. In 3 eyes, 1 in the LASIK group and 2 eyes in the LASeK group, the laser treatment had to be repeated before the target refraction and visual acuity could be achieved.

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discussion

In our study we show that both LASIK and LASeK are effective in treating small residual refractive errors after refractive lens exchange. The difference between both the UCDA and BCDA pre-operatively versus the post-operative UCDA was clinically as well as statistically significant. In some patients (3 eyes) more than 1 procedure was needed to reach emmetropia. No severe adverse events were seen in the study group.

A review of the literature shows that multifocal lenses are effective in restoring far and near vision in patients with cataract and also in clear lens extraction13-16. Patient satisfaction depends on how well maximal uncorrected visual acuity was achieved. With the current IOL technology small residual errors are the leading cause of dissatisfaction,1, 17 whereas only a few years ago the main limitation was the photic phenomena caused by the older generation multifocal IOL’s. 15 Motivation is an important factor in satisfaction after multifocal IOL implantation and acceptance of visually disturbing phenomena.14 The only factor that can be improved after implantation is treatment of the residual refractive error.

LASIK and LASeK have been shown to be predictable and safe after cataract surgery with monofocal lens implantations. 2-4, 6, 8-11, 18 There are few reports of LASIK and LASeK for residual errors after multifocal IOL implantation and overall the results are good.19-21

Predictability is another issue that plays a role in the decision to treat small residual refractive errors after a multifocal IOL implantation.

In our study the results of LASIK and LASeK were clinically and statistically similar. Treatment resulted in a decrease in the refractive error, and an increase in the UCDA. Review of the literature shows the residual refractive error being higher than the refractive error that we decided to treat. In contrast to the study done by Piñero et al22, we did not divide the treatments into hyperopic and myopic treatments, because of the small refractive error to be treated. In the mentioned study the predictability of the hyperopic treatments was lower than of the myopic treatments, however there was a mix of several multifocal lenses with different technologies of multifocality and also no mention of which laser treatment nomogram was used.22 In our study the number of eyes was not large enough to come to such conclusions, and the overall results were very good, with a high patient satisfaction. Some of these studies used wavefront treatments to reduce the residual refractive error.19-21 Wavefront measurements are in our experience problematic with the Hartmann-Shack technology, this is in accordance with the literature.22-24 A wavefront measurement with a dilated pupil will also measure aberrations that are beyond the 6 mm optic of the IOL, and these aberrations when corrected on the central cornea can in our opinion not lead to good visual and refractive results. In our study the results of standard laser treatments are acceptable, and lead to an improved UCDA, UCNA, and patient satisfaction.

Time between the IOL procedure and the bioptics procedure is different between the different studies. Macsai in her excellent review states that most authors consider 6-12 weeks to be the minimum time span to have the cornea wounds stabilize before

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proceeding with LASIK.25 We prefer to defer treatment until we have stability in complaints. The stability of the operative wounds of the RLe is one argument, but in our experience early post-operative tear-film disturbances as caused by lens surgery and prolonged eye-drop therapy causes fluctuating vision in the first few months. The mean time to surgery was nearly 6 months while in a few patients, in whom the bioptics procedure was planned before RLe, we went ahead as early as 13 weeks. At 3-6 months most complaints relating to dysphotopsias and halos have usually abated, and neuroadaptation has had time to take place.

In our patients none of the patients had a posterior capsulotomy done before the laser procedure. Usually the motivation for early posterior capsulotomy is to enhance stability of the refraction, which can possibly be upset by IOL movement following posterior capsulotomy. In our opinion posterior capsulotomies should only be done for clinically significant visual complaints. These complaints may be contrast related (patients often describe this as seeing through a plastic sandwich bag). Often near visual acuity decreases first and faster than far acuity, and can be tested by refracting them with the near Se refraction put in for far. If there is a discrepancy, near vision worse than far, this supports the diagnosis that the PCO is visually significant.

In conclusion: Standard laser ablation following RLe, by way of LASIK or LASeK results in better UCDA and better UVNA in a predictable and safe manner. More study is needed to enhance effectiveness and predictability of this procedure.

references

1. Lee eS, Lee SY, Jeong SY, Moon YS, Chin HS, Cho SJ, Oh J.H. effect of postopera-tive refractive error on visual acuity and pa-tient satisfaction after implantation of the Array multifocal intraocular lens. J Cataract Refract Surg. 2005 Oct;31(10):1960-5.

2. Leccisotti A. Secondary procedures after presbyopic lens exchange. J Cataract Re-fract Surg. 2004 Jul;30(7):1461-5.

3. Velarde JI, Anton PG, de Valentin-Gamazo L. Intraocular lens implantation and laser in situ keratomileusis (bioptics) to correct high myopia and hyperopia with astigma-tism. J Refract Surg. 2001 Mar-Apr;17(2 Suppl):S234-7.

4. Zaldivar R, Oscherow S, Piezzi V. Biopt-ics in phakic and pseudophakic intraocu-lar lens with the Nidek eC-5000 excimer laser. J Refract Surg. 2002 May-Jun;18(3 Suppl):S336-9.

5. Leccisotti A. Bioptics: where do things stand? Curr Opin Ophthalmol. 2006 Aug;17(4):399-405.

6. Maloney RK, Chan WK, Steinert R, Hersh P, O’Connell M. A multicenter trial of pho-

torefractive keratectomy for residual myo-pia after previous ocular surgery. Summit Therapeutic Refractive Study Group. Oph-thalmology. 1995 Jul;102(7):1042-52; dis-cussion 52-3.

7. Raman S, Redmond R. Reasons for second-ary surgical intervention after phacoemul-sification with posterior chamber lens im-plantation. J Cataract Refract Surg. 2003 Mar;29(3):513-7.

8. Artola A, Ayala MJ, Claramonte P, Perez-Santonja JJ, Alio JL. Photorefractive kera-tectomy for residual myopia after cataract surgery. J Cataract Refract Surg. 1999 Nov;25(11):1456-60.

9. Ayala MJ, Perez-Santonja JJ, Artola A, Claramonte P, Alio JL. Laser in situ keratomileusis to correct residual myopia after cataract surgery. J Refract Surg. 2001 Jan-Feb;17(1):12-6.

10. Kuo IC, O’Brien TP, Broman AT, Ghajar-nia M, Jabbur NS. excimer laser surgery for correction of ametropia after cataract surgery. J Cataract Refract Surg. 2005 Nov;31(11):2104-10.

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11. Norouzi H, Rahmati-Kamel M. Laser in situ keratomileusis for correction of induced astigmatism from cataract surgery. J Re-fract Surg. 2003 Jul-Aug;19(4):416-24.

12. Pop M, Payette Y, Amyot M. Clear lens ex-traction with intraocular lens followed by photorefractive keratectomy or laser in situ keratomileusis. Ophthalmology. 2001 Jan;108(1):104-11.

13. Lane SS, Morris M, Nordan L, Packer M, Tarantino N, Wallace RB, 3rd. Multifocal intraocular lenses. Ophthalmol Clin North Am. 2006 Mar;19(1):89-105, vi.

14. Leyland M, Zinicola e. Multifocal versus monofocal intraocular lenses after cataract extraction. Cochrane Database Syst Rev. 2003(3):CD003169.

15. Packer M, Fine IH, Hoffman RS. Refractive lens exchange with the array multifocal intraocular lens. J Cataract Refract Surg. 2002 Mar;28(3):421-4.

16. Werner L, Olson RJ, Mamalis N. New tech-nology IOL optics. Ophthalmol Clin North Am. 2006 Dec;19(4):469-83.

17. Blaylock JF, Si Z, Aitchison S, Prescott C. Visual function and change in quality of life after bilateral refractive lens exchange with the ReSTOR multifocal intraocular lens. J Refract Surg. 2008 Mar;24(3):265-73.

18. Guell JL, Gris O, de Muller A, Corcostegui B. LASIK for the correction of residual re-fractive errors from previous surgical pro-cedures. Ophthalmic Surg Lasers. 1999 May;30(5):341-9.

19. Alfonso JF, Fernandez-Vega L, Montes-Mico R, Valcarcel B. Femtosecond laser

for residual refractive error correction after refractive lens exchange with multifocal in-traocular lens implantation. Am J Ophthal-mol. 2008 Aug;146(2):244-50.

20. Jendritza BB, Knorz MC, Morton S. Wave-front-guided excimer laser vision correc-tion after multifocal IOL implantation. J Refract Surg. 2008 Mar;24(3):274-9.

21. Muftuoglu O, Prasher P, Chu C, Mootha VV, Verity SM, Cavanagh HD, Bowman R. W.McCulley, J. P. Laser in situ keratomi-leusis for residual refractive errors after apodized diffractive multifocal intraocular lens implantation. J Cataract Refract Surg. 2009 Jun;35(6):1063-71.

22. Pinero DP, espinosa MJ, Alio JL. LASIK Outcomes Following Multifocal and Monofocal Intraocular Lens Implantation. J Refract Surg. 2009 Nov 11:1-9.

23. Charman WN, Montes-Mico R, Radhakrish-nan H. Problems in the measurement of wavefront aberration for eyes implanted with diffractive bifocal and multifocal in-traocular lenses. J Refract Surg. 2008 Mar;24(3):280-6.

24. Munoz G, Albarran-Diego C, Sakla HF. Va-lidity of autorefraction after cataract sur-gery with multifocal ReZoom intraocular lens implantation. J Cataract Refract Surg. 2007 Sep;33(9):1573-8.

25. Macsai MS, Fontes BM. Refractive en-hancement following presbyopia-correcting intraocular lens implanta-tion. Curr Opin Ophthalmol. 2008 Jan;19(1):18-21.

STRAYLIGHT MeASUReMeNTS IN LASeR IN SITU KeRATOMILeUSIS AND LASeR-ASSISTeD SUBePITHeLIAL KeRATeCTOMY FOR MYOPIA

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STRAYLIGHT IN MYOPIC LASIK AND LASeK

purpose: To compare straylight values before and 3 months after laser in situ keratomileusis (LASIK) and laser-assisted subepithelial keratectomy (LASeK) and to analyze the causes of any change.

setting: Private refractive surgery clinic, Driebergen, The Netherlands.

methods: Straylight was measured before and after LASIK or LASeK with a C-Quant straylight meter; values were recorded as the straylight parameter log(s). Main outcome measures were the difference between postoperative and preoperative straylight values and factors causing a difference between the values.

results: The study evaluated 102 eyes having LASIK and 137 eyes having LASeK. On average, there was significant improvement in straylight values postoperatively in both groups. The mean decrease was 0.016 log(s) in the LASIK group and 0.026 log(s) in the LASeK group. Nonparametric testing (sign test) showed that the improvement in straylight was statistically significant in more than 50% of eyes in both groups. Straylight improved in 62 eyes in the LASIK group (P<.001) and 78 eyes in the LASeK group (P<.02) and deteriorated in 35 eyes and 58 eyes, respectively. There was an increase in straylight in 17 eyes (7.1%). Clinical correlations were found in some eyes that had increased postoperative straylight values.

conclusion: On average, straylight values 3 months after LASIK and LASeK were slightly decreased from baseline values. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.

ruth lapid-gortzak, md, Jan Willem van der linden, b optom, ivanka J.e. van der meulen, md,carla p. nieuwendaal, md, tom J.t.p. van den berg, phd

From a private refractive surgery clinic (Lapid-Gortzak, van der Meulen, van der Linden), Driebergen; the Department of Ophthalmology (Lapid-Gortzak, van der Meulen, Nieuwendaal), Cornea and Anterior Segment Service, Academic Medical Center, University of Amsterdam; Netherlands Institute for Neuroscience (van den Berg), Royal Academy of Arts and Sciences, Amsterdam, The Netherlands.

Journal of Cataract Refractive Surgery, 2010 Mar;36(3):465-471

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Refractive surgery is an accepted method of correcting refractive errors such as myopia. The accepted outcome measures of excimer laser refractive surgery are uncorrected distance visual acuity (UDVA), efficacy, safety, and stability of the refraction after the procedure.1,2

Quality of vision is difficult to define by a single parameter. Some patients are dissatisfied with the quality of vision after excimer laser refractive surgery even though their Snellen acuity is 20/20 (1.0) or better. Higher-order aberrations, image degradation, and contrast acuity have been implicated as reasons for patient dissatisfaction.3 Glare disability is another parameter that correlates with visual complaints after refractive surgery.4

All light reaching the eye is scattered to some extent when passing through the structures of the eye. This causes a veil of light over the visual image, resulting in degraded vision. This veil of light is called straylight. Straylight defines the functional effect of scatter and is a means of objective quantification.5,6 Straylight is a functional measure of the effect of light spreading over the retina; the term is used by the Commission Internationale d’eclairage (CIe) to define disability glare. The amount of straylight is expressed as the straylight parameter; that is, as log(s). Glare disability, which is the reduction in visual performance caused by a glare source, causes retinal contrast degradation secondary to intraocular straylight.5–7 The most common example of a glare source is an oncoming headlight, resulting in a loss of contrast that degrades vision to a degree that the patient cannot see an object (eg, a car) that is right in front of her or him.5–8

We prospectively measured straylight preoperatively and postoperatively with a straylight meter to study the behavior of the straylight parameter in patients having myopic excimer laser surgery. Intrastromal ablations (laser in situ keratomileusis [LASIK]) and surface ablations (laser-assisted subepithelial keratectomy [LASeK]) were included. The excimer laser used in refractive surgery disrupts the normal structure of the cornea; the collagen fibers of the cornea are lined up at specific intervals so that light rays pass undisturbed through the cornea and arrive at the media of the eye.9–13 Disruption of the corneal structure can occur in LASIK because the edges of the cut stroma return to a new position of apposition. In LASeK, the corneal tissue responds to the treatment with changes in the cellular structure and fibrillar organization, which can increase straylight; this may be an additional effect in LASIK as well. In both types of treatment, keratocytes undergo ultrastructural changes that may contribute to a change in straylight.9–12,14 Based on this assumption, we expected an increase in straylight after excimer laser refractive surgery.

patients and methods

This consecutive prospective case series comprised eyes having refractive excimer laser surgery for myopia. enrollment in the study occurred with informed consent. The tenets of the Declaration of Helsinki were followed. Assignment to LASIK or LASeK

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was performed according to the consensus of the Netherland Society for Refractive Surgery (2006) and patient preference.

All eyes had a full ophthalmologic examination preoperatively. The evaluation included UDVA, corrected distance visual acuity (CDVA), manifest and cycloplegic refractions, slitlamp examination, dilated fundoscopy, topography, noncontact pachymetry, wavefront aberrometry, tonometry, and straylight measurement. Visual acuity was tested in 3m condensed lanes using the early Treatment Diabetic Retinopathy Study chart in metric units. The 3-month postoperative examination included UDVA, CDVA, keratometry, tonometry, biomicroscopy, and straylight measurement.

Laser in situ keratomileusis was performed using an XP 120 microkeratome and a 100z excimer laser (both Bausch & Lomb). Laser-assisted subepithelial keratectomy was performed with a 20% ethanol solution, 30-second exposure time, and the same laser equipment used in LASIK cases. In LASeK cases in which the ablation was deeper than 100 µm, mitomycin-C (MMC) 0.02% was applied for 12 seconds and then rinsed with 30 cc of a balanced salt solution; additional appropriate informed consent was obtained in these cases.

Postoperatively, LASIK patients were treated with nonpreserved hourly sodium hyaluronic acid 0.1% eyedrops and tobramycin 0.3%–dexamethasone 0.1% given 3 times a day. The combination drops were stopped after 3 days. The artificial tears were continued for at least 3 months, during which time they were tapered. In LASeK patients, the postoperative treatment consisted of a bandage contact lens for 3 days with concomitant unpreserved artificial tears, tobramycin 0.3% eyedrops 3 times a day, and oral analgesic agents as needed. After the contact lens was removed 3 days postoperatively, the antibiotic agent was changed to chloramphenicol 0.4% ointment 4 times daily for 4 additional days. Fluorometholone 0.1% eyedrops were started 8 days postoperatively and taken daily until 21 days. Artificial tears were used hourly and tapered until 3 months.

Undilated straylight measurements were performed twice preoperatively and twice 3 months postoperatively using a C-Quant straylight meter (Oculus Optikgeraete GmbH). The system and its parameters have been described.13,15 The straylight meter measures forward light scatter in the eye. It provides direct information about optical imperfections causing glare disability and determines straylight values according to the internationally accepted definition by CIe.5 An expected standard deviation (eSD) was developed to control and enhance the internal reliability of the test.15 Only reliable test results with an eSD less than 0.08 log units were accepted. each measurement was repeated to arrive at an independent measure of reliability. Measurements were performed under ambient light by the same technician with corrective refraction performed with a meticulously kept set of trial lenses according to the manufacturer’s instructions. The straylight results of the meter were recorded on a logarithmic scale as log(s).15 A difference of 0.3 in log(s) corresponds to a difference in straylight intensity of a factor of 2.

Repeatability of the measurements was tested. Although the test used in the straylight meter (compensation comparison paradigm) is designed to eliminate bias, evaluation was performed to determine whether there was a learning effect. Thus, the

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first measurements were repeated and the second measurement and first measurement compared. These data also provided an independent measure of repeatability to be compared with the eSD values given by the straylight meter.

Outcome measures were straylight values and whether there was a correlation between the values and factors such as slitlamp findings, ablation depth, and the use of MMC. Patient records were reviewed to find indications for changes between preoperatively and postoperatively. efficacy (postoperative UDVA divided by preoperative CDVA) and safety (postoperative CDVA divided by preoperative UDVA) were other outcome measures.

Statistical analysis was performed using SPSS software (version 16, SPSS, Inc.). Results were analyzed by t tests and 1-sided nonparametric sign and Mann-Whitney tests. The significance level was 5%.

results

Two hundred thirty-nine eyes of 145 patients were tested; 102 eyes had LASIK and 137 eyes, LASeK. The mean age of the patients was 38.6 years (range 20 to 60 years). The mean preoperative spherical equivalent (Se) was -3.11 diopters (D) (range -0.75 to -7.00 D) in the LASIK group and-3.88 D (range-0.75 to -9.50 D) in the LASeK group. Mitomycin-C was used in 31 eyes in the LASeK group. These eyes had a mean preoperative Se refraction of -5.70 D (range -1.62 to -9.50 D).

Table 1 shows the postoperative outcomes in all eyes and by group. One eye (1%) in the LASIK group and 5 eyes (3.6%) in the LASeK group lost 2 or more lines of CDVA from the preoperative value.

Figure 1 shows the preoperative versus postoperative straylight values in the LASIK group. The mean decrease was 0.016 log(s) + 0.172 (SD), which was not statistically significant (P<.05, paired t test). Twelve eyes had an increase in straylight of more than 0.2 log units. A clinical correlation (microstriae in the LASIK flap in 5 eyes and interface debris in 2 eyes) was found in 7 eyes. In the remaining 5 eyes, the cornea did not show changes on biomicroscopy. The straylight was decreased by more than 0.2 log units in 11 eyes the LASIK group, all of which had a normal biomicroscopic examination.

table 1: Postoperative outcomes.

groupmean ucVa (snellen) efficacy safety

Within +0.50 d* (%)

se refraction (d) mean + sd range

All cases 1.23 (20/15) 1.16 1.19 96.6 - -

LASIK 1.18 (20/16) 1.13 1.18 95.1 +0.17 + 0.27 -0.50 to +1.50

LASeK 1.25 (20/15) 1.18 1.20 97.8 +0.03 + 0.22 -0.50 to +1.00

LASeK + MMC 1.15 (20/17) 1.16 1.12 - -0.01 + 0.49 -0.75 to +1.25

LASeK = laser-assisted subepithelial keratectomy; LASIK = laser in situ keratomileusis; MMC = mitomycin-C; UDVA = uncorrected visual acuity

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One patient in the LASIK group had grade II diffuse lamellar keratitis (DLK); however, the patient had a complete recovery and a low postoperative log(s) value. Preoperatively, mean log(s) straylight value was 1.02 log(s) in the right eye and 1.16 log(s) in the left eye. The postoperative values were to 0.85 log(s) and 0.86 log(s), respectively.

Figure 2 shows the preoperative versus postoperative straylight values in the LASeK group. The mean decrease of 0.026 + 0.141 log(s) was statistically significant (P<.02, paired t test). Five eyes had an increase in straylight of more than 0.2 log units. In 4 eyes, trace haze was noted in the charts postoperatively. One eye had a scar from a postoperative corneal foreign-body injury that occurred 6 days postoperatively. In the 14 eyes with a decrease in straylight of more than 0.2 log(s), slitlamp examination did show abnormalities.

Figure 3 shows the preoperative versus postoperative straylight values in the 31 LASeK eyes treated with MMC. The mean decrease was 0.056 + 0.164 log(s), which was significantly greater than in the LASeK group as a whole (P<.05, paired t test).

Compared with values in a normal population, the baseline measurement in the LASIK and LASeK eyes was increased by a mean of 0.06 log(s) (P<.001). evaluation of postoperative results versus preoperative results showed that this increase did not influence the comparative results.

4 Straylight Measurements in LASIK and LASEK for Myopia

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Group Mean UCVA (Snellen)

Efficacy Safety Within +0.50 D* (%)

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All cases 1.23 (20/15)

1.16 1.19 96.6 - -

LASIK 1.18 (20/16)

1.13 1.18 95.1 +0.17 + 0.27 -0.50 to +1.50

LASEK 1.25 (20/15)

1.18 1.20 97.8 +0.03 + 0.22 -0.50 to +1.00

LASEK + MMC

1.15 (20/17)

1.16 1.12 - -0.01 + 0.49 -0.75 to +1.25

LASEK = laser-assisted subepithelial keratectomy; LASIK = laser in situ keratomileusis; MMC = mitomycin-C; UDVA = uncorrected visual acuity Table 1: Postoperative outcomes.

Figure 1. Postoperative versus preoperative straylight values in the LASIK group.

Figure 2. Postoperative versus preoperative straylight measurements in the LASEK group.

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Group Mean UCVA (Snellen)

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All cases 1.23 (20/15)

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LASIK 1.18 (20/16)

1.13 1.18 95.1 +0.17 + 0.27 -0.50 to +1.50

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LASEK + MMC

1.15 (20/17)

1.16 1.12 - -0.01 + 0.49 -0.75 to +1.25

LASEK = laser-assisted subepithelial keratectomy; LASIK = laser in situ keratomileusis; MMC = mitomycin-C; UDVA = uncorrected visual acuity Table 1: Postoperative outcomes.

Figure 1. Postoperative versus preoperative straylight values in the LASIK group.

Figure 2. Postoperative versus preoperative straylight measurements in the LASEK group.

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Figure 3. Postoperative versus preoperative straylight values in eyes treated with MMC.

Figure 4. Differences between the first and the second straylight measurements preoperatively and postoperatively. Compared with values in a normal population, the baseline measurement in the LASIK and LASEK eyes was increased by a mean of 0.06 log(s) (P<.001). Evaluation of postoperative results versus preoperative results showed that this increase did not influence the comparative results.

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figure 1. Postoperative versus preoperative straylight values in the LASIK group.

figure 2. Postoperative versus preoperative straylight measurements in the LASEK group.

figure 3. Postoperative versus preoperative straylight values in eyes treated with MMC.

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104

Figure 3. Postoperative versus preoperative straylight values in eyes treated with MMC.

Figure 4. Differences between the first and the second straylight measurements preoperatively and postoperatively. Compared with values in a normal population, the baseline measurement in the LASIK and LASEK eyes was increased by a mean of 0.06 log(s) (P<.001). Evaluation of postoperative results versus preoperative results showed that this increase did not influence the comparative results.

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figure 4. Differences between the first and the second straylight measurements preoperatively and postoperatively.

The repeatability evaluation showed a mean difference between the first and second straylight measurement of 0.009 + 0.079 log(s) preoperatively and 0.007 + 0.078 log(s) postoperatively (Figure 4). Neither difference was statistically significant; thus, there was no learning effect.

Figures 1 to 3 suggest that the distribution of the postoperative and preoperative differences between measurements did not conform to a normal Gaussian distribution. Thus, nonparametric testing was performed and showed that the straylight value was statically significantly better in more than 50% of eyes in both groups. The straylight value improved in 62 eyes in the LASIK group (P<.001) and in 78 eyes in the LASeK group (P<.02) and decreased in 35 eyes and 58 eyes, respectively.

Figure 5 and Figure 6 show straylight changes as a function of ablation depth in the LASIK group and LASeK group, respectively. Ablation depth correlated positively with a decrease in straylight in groups. However, the correlations were not statistically significant. In the LASeK group, comparison of eyes with MMC and eyes without MMC with and without ablation depth as covariate showed no significant differences.

discussion

excimer laser refractive surgery is an accepted method of treating refractive errors. In general, postoperative UDVA, predictability, and safety results have been good. However, postoperative quality of vision remains a subject of ongoing discussion, and its parameters are not standardized.3 Different tests yield different results and are usually performed under nonstandardized conditions. The straylight meter used in the present study is reported to give reliable and repeatable measurements of forward scatter in the eye.16 This scatter is a measure of glare disability, which is becoming an important parameter of quality of vision not only in refractive surgery but also in other situations (eg, night driving, cataract surgery, contact lens wear).

In our study, we surprisingly found that on average, straylight (ie, glare disability) was reduced after LASIK and LASeK. Nonparametric testing showed that the decrease was statistically significant in more than 50% of cases. The finding is even more striking

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considering that some patients on slitlamp examination had haze or interlamellar debris, which can negatively affect straylight values. These results suggest that negative as well as positive results can occur in refractive surgery. The balance between the 2 effects determines the balance of the overall outcome. In fact, findings in studies in which straylight changes were, on average, minimal might be better understood on the basis of this finding. In a 1996 study, Schallhorn at al.17 evaluated 30 eyes that had photorefractive keratectomy (PRK) but no change in straylight, a finding the authors found surprising. Other studies in the 1990s12,17,18 found no increase in straylight after laser refractive surgery in general; as in our study, increased straylight values were found on an individual basis.

In a study of PRK and LASIK, Beerthuizen et al.19 found that there was generally no significant change in straylight values 1 month postoperatively; however, several patients with increased straylight measurements had microstriae, interface debris, or haze. We also found a clinical correlation between increased straylight measurements and flap-related issues and haze. On the other hand, Beerthuizen et al. found increased straylight values in cases without clinical signs or symptoms to explain the increase; this also occurred in our study. Results in a study by Vignal et al.4 suggest that this can occur. Although they found no definite effect of straylight on clinical parameters, they found a correlation between postoperative glare complaints and increased straylight measurements. Vignal et al. also found that patients with improved contrast sensitivity had no increase in straylight values. Furthermore, patients with no visual complaints had lower straylight values than patients with night-vision complaints. We did not correlate straylight measurements with patient complaints. At our clinic, patients complete a voluntary questionnaire 3 months after surgery; however, the questionnaire does not include glare symptoms. We did not specifically evaluate night-vision disturbances preoperatively or postoperatively; therefore, we cannot correlate straylight outcomes


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The repeatability evaluation showed a mean difference between the first and second straylight measurement of 0.009 + 0.079 log(s) preoperatively and 0.007 + 0.078 log(s) postoperatively (Figure 4). Neither difference was statistically significant; thus, there was no learning effect. Figures 1 to 3 suggest that the distribution of the postoperative and preoperative differences between measurements did not conform to a normal Gaussian distribution. Thus, nonparametric testing was performed and showed that the straylight value was statically significantly better in more than 50% of eyes in both groups. The straylight value improved in 62 eyes in the LASIK group (P<.001) and in 78 eyes in the LASEK group (P<.02) and decreased in 35 eyes and 58 eyes, respectively. Figure 5 and Figure 6 show straylight changes as a function of ablation depth in the LASIK group and LASEK group, respectively. Ablation depth correlated positively with a decrease in straylight in groups. However, the correlations were not statistically significant. In the LASEK group, comparison of eyes with MMC and eyes without MMC with and without ablation depth as covariate showed no significant differences.

Figure 5. Relationship between straylight Figure 6. Relationship between straylight values and ablation depth in the LASIK group values and ablation depth in the LASEK (r = -0.093, not significant). group (r = -0.085, not significant). DISCUSSION Excimer laser refractive surgery is an accepted method of treating refractive errors. In general, postoperative UDVA, predictability, and safety results have been good. However, postoperative quality of vision remains a subject of ongoing discussion, and its parameters are not standardized.3 Different tests yield different results and are usually performed under nonstandardized conditions. The straylight meter used in the present study is reported to give reliable and repeatable measurements of forward scatter in the eye.16 This scatter is a measure of glare disability, which is becoming an important parameter of quality of vision not only in refractive surgery but also in other situations (eg, night driving, cataract surgery, contact lens wear). In our study,we surprisingly found that on average, straylight (ie, glare disability) was reduced after LASIK and LASEK. Nonparametric testing showed that the decrease was

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The repeatability evaluation showed a mean difference between the first and second straylight measurement of 0.009 + 0.079 log(s) preoperatively and 0.007 + 0.078 log(s) postoperatively (Figure 4). Neither difference was statistically significant; thus, there was no learning effect. Figures 1 to 3 suggest that the distribution of the postoperative and preoperative differences between measurements did not conform to a normal Gaussian distribution. Thus, nonparametric testing was performed and showed that the straylight value was statically significantly better in more than 50% of eyes in both groups. The straylight value improved in 62 eyes in the LASIK group (P<.001) and in 78 eyes in the LASEK group (P<.02) and decreased in 35 eyes and 58 eyes, respectively. Figure 5 and Figure 6 show straylight changes as a function of ablation depth in the LASIK group and LASEK group, respectively. Ablation depth correlated positively with a decrease in straylight in groups. However, the correlations were not statistically significant. In the LASEK group, comparison of eyes with MMC and eyes without MMC with and without ablation depth as covariate showed no significant differences.

Figure 5. Relationship between straylight Figure 6. Relationship between straylight values and ablation depth in the LASIK group values and ablation depth in the LASEK (r = -0.093, not significant). group (r = -0.085, not significant). DISCUSSION Excimer laser refractive surgery is an accepted method of treating refractive errors. In general, postoperative UDVA, predictability, and safety results have been good. However, postoperative quality of vision remains a subject of ongoing discussion, and its parameters are not standardized.3 Different tests yield different results and are usually performed under nonstandardized conditions. The straylight meter used in the present study is reported to give reliable and repeatable measurements of forward scatter in the eye.16 This scatter is a measure of glare disability, which is becoming an important parameter of quality of vision not only in refractive surgery but also in other situations (eg, night driving, cataract surgery, contact lens wear). In our study,we surprisingly found that on average, straylight (ie, glare disability) was reduced after LASIK and LASEK. Nonparametric testing showed that the decrease was

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myopes lasek

figure 5. Relationship between straylight values and ablation depth in the LASIK group (r = -0.093, not significant).

figure 6. Relationship between straylight values and ablation depth in the LASEK group (r = -0.085, not significant).

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with patient-reported clinical symptoms (ie, whether patients were aware of changes in straylight).

In some cases of increased straylight, we saw a physical finding on biomicroscopy (eg, microstriae of the flap, haze, interface debris) that might explain the increase.

Microstriae can reduce contrast sensitivity20 and have been implicated in the increase in straylight after LASIK.19 A 1995 study of PRK by Veraart et al.12 found increased straylight values after reepithelialization in the early postoperative period; the straylight measurements slowly return to baseline within months except in cases of severe haze. There are several reports of haze as a cause for increased straylight values,12,19 and we found this to be true in several cases. The use of MMC reduces the incidence of severe haze and results in lower straylight values because straylight is a parameter of corneal clarity, and it may correlate well with cellular responses to MMC.11

Other factors that might increase straylight measurements were excluded in our study. The trial lenses we used were kept meticulously clean according to the operator’s manual. Pachymetry and tonometry were performed with noncontact instruments; thus, direct physical contact and disturbance of the corneal epithelium are excluded causes of the relatively increased preoperative straylight values compared with those in the normal population.

Studies of backscatter9,10 report increased light scattering from the cornea after laser refractive surgery. However, backscatter is not equivalent to forward scatter as measured by the straylight meter we used. Backscatter correlates well with haze. In LASIK, backscatter is related to the edges of the LASIK flap. Backscatter is significantly lower in LASIK than in LASeK.9,10 Increased straylight after radial keratotomy has been reported,21 which is not surprising because the technique intentionally induces corneal scarring to reshape the prolate cornea.

The reason for our finding of a potential decrease in straylight as a result of laser refractive surgery is puzzling. First, measurements were taken 3 months postoperatively; it is generally accepted that by this time, healing is almost complete and refraction has stabilized.

We expected an increase in straylight as a result of disruption of the fibers and cells of the cornea.9–11 One consideration is whether the preoperative straylight values in our patients were relatively high. Most patients were wearing contact lenses up to a few days before preoperative testing. Contact lens wear can cause increased straylight measurements, even after the lenses have not been worn for a while (I.J.e. van der Meulen, personal communication, December 2008). Thus, the history of contact lens wear may be why our patients had a 0.06 log(s) increase over values in the normal population.

Another consideration is that the reduction in straylight reflects an effect in the cornea itself. In the young normal eye, a substantial part of straylight originates from the cornea.6 Perhaps removing part of the cornea decreases its influence as a source of straylight. We studied the relationship between straylight and ablation depth. Roughly one third of ocular straylight can be attributed to corneal sources. If a maximum of 20% of the cornea were ablated, the total contribution to straylight decrease would be

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on the order of one fifteenth of the total ocular straylight. On a logarithmic scale, this amounts to 0.03 log units. Although this is a small number, it may be significant (mean value 0.016 in LASIK group and 0.026 in LASeK group). On an individual basis, such a change is hard to detect. We also found that deeper ablations were correlated with a greater decrease in straylight values in both groups. Although the finding was not statistically significant, it may indicate that ablation depth is the most important factor in reducing straylight. The use of MMC may mitigate the effect of ablation depth on straylight reduction because of the tissue response it evokes.

Another potential cause for the unexpected finding of decreased straylight after LASIK and LASeK may be that corneal hydration can change in vitro and in vivo, as reported by Patel et al.22 Corneal hydration is related to corneal transparency and thus to visual function.23 Perhaps the workload of the endothelium decreases based on ablation of tissue that otherwise must be kept dehydrated and, therefore, the stromal tissue becomes less hydrated, decreasing straylight.

Other factors that might have affected our results are pupil size, a change in the refractive index, and tear-film changes. Straylight is weakly dependent on pupil sizes between 2.0 mm and 8.0 mm in the normal population. In our study, the expected difference would be on the order of 0.01 log(s) assuming a change of 0.5 mm.24 We did not assess the influence of tear-film, although it is related to preoperative contact lens wear. Moreover, the tear-film would have likely recovered by the time the postoperative measurements were taken in our study.

The repeatability evaluation showed that the learning curve of the testing was not a source of bias. The mean difference between the first and second straylight measurement was 0.009 + 0.079 log(s) preoperatively and 0.007 + 0.078 log(s) postoperatively.

In conclusion, on average, 3 months after myopic laser refractive surgery, straylight was reduced. Most cases of increased straylight were related to clinical findings such as microstriae, debris, or haze. Additional studies are needed to corroborate the positive finding and correlate it with physical phenomena in the cornea. Although straylight has a role as an objective parameter of quality of vision in laser refractive surgery, the correlation between the findings and patients’ subjective quality of vision must be evaluated.

references1. Shortt AJ, Allan BD. Photorefractive kera-

tectomy (PRK) versus laser-assisted in-situ keratomileusis (LASIK) for myopia. CochraneDatabase Syst Rev 2006; (2): CD005135

2. Shortt AJ, Bunce C, Allan BDS. evidence for superior efficacy and safety of LASIK over photorefractive keratectomy for cor-rection of myopia. Ophthalmology 2006; 113:1897–1908

3. Fan-Paul NI, Li J, Sullivan Miller J, Floralis GJ. Night vision disturbances after corneal refractive surgery. Surv Ophthalmol 2002; 47:533–546

4. Vignal R, Tanzer D, Brunstetter T, Schall-horn S. Lumière diffractée et sensibilité à l’éblouissement après PKR et LASIK guidés par front d’onde. [Scattered light and glare sensitivity after wavefront-guided pho-torefractive keratectomy (WFG-PRK) and

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laser in situ keratomileusis (WFG-LASIK)]. J Fr Ophtalmol 2008; 31:489–493

5. Vos JJ. Disability glare; a state of the art report. CIe J 1984; 3(2):39–53

6. van den Berg TJTP. Analysis of intraocular straylight, especially in relation to age. Op-tom Vis Sci 1995; 72:52–59

7. van den Berg TJTP. On the relation be-tween glare and straylight. Doc Ophthal-mol 1991; 78:177–181

8. Aslam TM, Haider D, Murray IJ. Principles of disability glare measurement: an oph-thalmological perspective. Acta Ophthal-mol Scand 2007; 85:354–360

9. Jain S, Khoury JM, Chamon W, Azar DT. Corneal light scattering after laser in situ keratomileusis and photorefractive keratec-tomy. Am J Ophthalmol 1995; 120:532–534

10. Chang S-W, Benson A, Azar DT. Corneal light scattering with stromal reformation after laser in situ keratomileusis and pho-torefractive keratectomy. J Cataract Re-fract Surg 1998; 24:1064–1069

11. Kim T-I, Pak JH, Lee SY, Tchah H. Mitomy-cin C-induced reduction of keratocytes and fibroblasts after photorefractive kera-tectomy. Invest Ophthalmol Vis Sci 2004; 45:2978–2984. Available at: http://www.iovs.org/cgi/reprint/45/9/2978. Accessed November 15, 2009

12. Veraart HGN, van den Berg TJTP, Hen-nekes R, Adank AMJ. Stray light in pho-torefractive keratectomy for myopia. Doc Ophthalmol 1995; 90:35–42

13. Franssen L, Coppens Je, van den Berg TJTP. Compensation comparison method for assessment of retinal straylight. Invest Ophthalmol Vis Sci 2006; 47:768–776. Available at: http://www. iovs.org/cgi/re-print/47/2/768. Accessed November 25, 2009

14. Jain S, McCally RL, Connolly PJ, Azar DT. Mitomycin C reduces corneal light scat-tering after excimer keratectomy. Cornea 2001; 20:45–49

15. Coppens Je, Franssen L, van den Berg TJTP. Reliability of the compensation com-parison method for measuring retinal stray

light studied using Monte-Carlo simula-tions. J Biomed Opt 2006; 11:054010

16. Cerviño A, Montes-Mico R, Hosking SL. Performance of the compensation com-parison method for retinal straylight mea-surement: effect of patient’s age on repeat-ability. Br J Ophthalmol 2008; 92:788–791

17. Schallhorn SC, Blanton CL, Kaupp Se, Sut-phin J, Gordon M, Goforth H Jr, Butler FK Jr. Preliminary results of photorefractive keratectomy in active-duty United States Navy personnel. Ophthalmology 1996; 103:5–21; discussion by LJ Maguire, 21–22

18. Butuner Z, elliott DB, Gimbel HV, Slimmon S. Visual function one year after excimer la-ser photorefractive keratectomy. J Refract Corneal Surg 1994; 10:625–630

19. Beerthuizen JJG, Franssen L, Landesz M, van den Berg TJTP. Straylight values 1 month after laser in situ keratomileusis and photorefractive keratectomy. J Cataract Refract Surg 2007; 33:779–783

20. Quesnel N-M, Lovasik JV, Ferremi C, Boi-leau M, Ieraci C. Laser in situ keratomile-usis for myopia and the contrast sensitiv-ity function. J Cataract Refract Surg 2004; 30:1209–1218

21. Veraart HGN, van den Berg TJTP, IJspeert JK, Cardozo OL. Stray light in radial kera-totomy and the influence of pupil size and straylight angle. Am J Ophthalmol 1992; 114:424–428

22. Patel S, Alió JL, Pérez-Santonja JJ. Refractive index change in bovine and human corneal stroma before and after LASIK: a study of untreated and re-treated corneas implicat-ing stromal hydration. Invest Ophthalmol Vis Sci 2004; 45:3523–3530. Available at: http://www.iovs.org/cgi/reprint/45/10/3523. Ac-cessed November 25, 2009

23. Zucker BB. Hydration and transparen-cy of corneal stroma. Arch Ophthalmol 1966; 75:228–231 24. Franssen L, Taber-nero J, Coppens Je, van den Berg TJTP. Pupil size and retinal straylight in the nor-mal eye. Invest Ophthalmol Vis Sci 2007; 48:2375–2382. http://www.iovs.org/cgi/reprint/48/5/2375. Available atAccessed November 25, 2009

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STRAYLIGHT BeFORe AND AFTeR HYPeROPIC LASIK AND LASeK

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STRAYLIGHT IN HYPeROPIC LASIK AND LASeK

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abstract

purpose: To compare straylight values pre-operatively and 3 months post-operatively in hyperopic laser in situ keratomileusis (LASIK) and laser assisted sub-epithelial keratomileusis (LASeK) and analyze the causes of change.

setting: Retina, Private refractive surgery clinic, Driebergen, the Netherlands.

methods: In 65 eyes undergoing LASIK (39 eyes) or LASeK (26 eyes) straylight was measured pre- and post-operatively with the C-Quant straylight meter, and recorded as log (s).

main outcome measures: Difference in post- versus pre-operative straylight values.

results: At 3 months post-operatively in LASIK (n=39 eyes) straylight increased slightly with log(s) 0.051 + 0.158 SD, and in LASeK (n=26 eyes) straylight also increased slightly with a mean of 0.031 + 0.146 log(s). Both were not statistically significant, but can be clinically significant in individual cases. In some eyes with increased straylight we found either haze or interface debris. Mean postoperative spherical equivalent refraction was -0.05D + 0.27D.

conclusion: Straylight, by definition the measure for glare disability, increases slightly after hyperopic LASIK and LASeK. The increase in straylight is statistically not significant. In some eyes with increased straylight haze and interface debris were seen. Not in all cases a cause for increased straylight could be found.

ruth lapid-gortzak md1,2, J.W. van der linden, b. optom1, ivanka van der meulen md1,2, carla p. nieuwendaal md2, maarten p. mourits md phd2 and, thomas J.t.p. van den berg phd3.

1 Retina Total Eye Care, Driebergen, the Netherlands; 2 Department of Ophthalmology, Academic Medical Center, University of Amsterdam, the Netherlands; 3 Institute for Neuroscience, Royal Academy for Arts and Science, Amsterdam, The Netherlands.

Journal of Cataract and Refractive Surgery, 2010, in Print.

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introduction

Quality of vision after corneal laser refractive surgery is not always related to Snellen acuity. Contrast acuity and sensitivity, glare, and higher order aberrations play a role in perception of vision.

For visual quality there is no single parameter or test. Forward scatter causes straylight, light that does not come to a focus on the retina, but is scattered in the eye by the ocular structures itself, which is a cause for glare. Retinal straylight by definition corresponds to glare disability.1 This is a parameter of visual quality that can be dependably and repeatably measured.2

The point spread function curve has different domains.3 The central most 1 degree of arc describes the effect of lower and higher order aberrations, which is the small angle, high intensity domain, and deviations in this domain may cause a decrease in visual acuity and contrast sensitivity. The wider domain beyond 1 degree of arc is the large angle low intensity domain, which is straylight. Clinically straylight corresponds to (disability) glare and haziness of vision.3

The C-Quant straylight meter (Oculus Optikgeraete GmbH, Wetzlar, Germany) measures straylight in the eye. It provides information about the optical imperfections as the cause for disability glare. Disability glare is the reduction in visual performance caused by a glare source, which causes retinal contrast degradation secondary to intraocular straylight.1, 4, 5 The C-Quant determines straylight according to the internationally accepted definition (Commission Internationale d’Éclairage CIe).1 Straylight is a functional measure for the effect of light spreading over the retina, introduced as the CIe definition for “disability glare”. The amount of straylight is expressed as the straylight parameters.

In corneal laser refractive surgery the assumption has been that straylight may increase after treatment. After corneal laser surgery corneal structure may be altered by changed alignment of the corneal fibrils, which have a precise arrangement essential for optical clarity (like in a crystal), or because of cellular changes and matrix changes after corneal laser surgery, and these changes could induce an increase in straylight post-operatively. 6-9

In myopic corneal laser surgery we surprisingly found a statistically significant decrease in straylight overall. In individual cases there may be an increase in straylight, which is related to clinical corneal findings, some of the time.10, 11 The decrease in straylight in the myopic treatments was found to be strongly correlated to the ablation depth. In hyperopes the deepest ablation profile is more peripheral on the cornea, beyond the pupil opening. Because the central cornea is barely affected by the ablation depth, we do not expect hyperopic treatments to show a decrease in straylight. In order to verify these results and the need to look at the behavior of straylight in hyperopia we compared straylight before and after hyperopic corneal laser surgery.

Some forms of hyperopia can be treated with LASIK and LASeK. Many studies pertaining to the visual outcomes, the efficacy and safety are in the literature. Hyperopia is more difficult to treat and does not achieve the same level of efficacy and

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safety as in myopic treatments.12-15 However, there are no data yet as to the behavior of straylight in hyperopic LASIK and LASeK. We report our data on straylight in hyperopic LASIK and LASeK.

methods

Consecutive prospective case series, of 65 eyes, of 33 patients, undergoing hyperopic refractive excimer laser surgery. enrollment into the study occurred with informed consent. The tenets of the Declaration of Helsinki were followed. All eyes had a full ophthalmologic examination pre-operatively: uncorrected (UDVA) and corrected distance visual acuity (CDVA), manifest and cycloplegic refraction, slit-lamp examination, dilated fundoscopy, topography and pachymetry, wavefront aberrometry, tonometry, mesopic pupillometry by the orbscan, scotopic pupillometry with the NoDIZy zywave (Technolas, Germany), and straylight measurement.

Visual acuity was tested in 3 meter condensed lanes, using the eTDRS chart, noted in metric units. Assignment to LASIK or LASeK was done according to the consensus of the Netherlands’ Society for Refractive Surgery (2006) and patient preference.

Laser in situ keratomileusis was performed using the XP 120 microkeratome (Technolas, Munich, Germany) and the Technolas 100z excimer laser (Technolas, Munich, Germany). Laser assisted subepithelial keratomileusis was performed with a 20% ethanol solution, 30 seconds exposure time and the same laser equipment. The nomogram utilized is the Planoscan standard ablation profile. The optical zone was chosen to be at least 0.7 mm larger than the mesopic pupil. The maximal ablation occurs 1.67 mm peripheral to the optical zone, so at a diameter 3.33 mm larger than the optical zone diameter. Post-operatively LASIK patients were treated with non-preserved hourly sodiumhyaluronic acid eye drops 0.1%, tobramycine 0.3% combined with dexamethasone 0.1% three times daily (tid). The combination drops were stopped after 3 days, artificial tears continued for at least 3 months, but tapered. In LASeK the post-operative treatment consisted of a bandage contact lens for 3 days, with concomitant unpreserved artificial tears, tobramycine 0.3% eye drops tid, and analgesics orally as needed. After the contact lens was removed on post-operative day (POD) 3, the antibiotic was changed for chloramphenicol 0.4% antibiotic ointment four times daily for 4 more days. Fluoromethalone 0.1% eye drops were started on POD 8 twice daily till POD 21. Artificial tears were used hourly and tapered till 3 months. At the three months post-operative visit examination included UDVA, CDVA, keratometry, tonometry, biomicroscopy, and straylight measurement.

Undilated straylight measurements were done twice pre-operatively and twice 3 months post-operatively with the C-Quant straylight meter. The patient performed a test of 2 alternative forced-choices, in which the patient had to choose between the stronger of 2 flickers presented in controlled background lights. The test duration is controlled by presenting a fixed number of stimuli. The straylight test has an internal analysis procedure which yields a reliability estimate called “expected Standard

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Deviation” (eSD).16 . This eSD was developed to control and enhance internal reliability of the test.16 Only reliable test results with an eSD of less than 0.08 log units were accepted. each measurement was repeated to arrive at an independent measure of reliability in the study. Measurements were performed under ambient lighting conditions with corrective refraction. The results of the straylight meter is recorded as the “straylight parameter” s, presented on a logarithmic scale as log(s).16 A difference of 0.3 in log(s) corresponds to a difference of a factor 2 in the intensity of straylight.4

Statistical analysis was done with the SPSS version 16. Significance level was chosen to be 5%. T-tests and the non-parametric sign and Mann-Whitney tests were used, one-sided, and indicated in the results.

results

In 65 eyes of 33 patients straylight was measured before and after hyperopic LASIK or LASeK.

Visual acuity outcomes

In the LASIK group:Thirty nine eyes of 20 patients had LASIK. Demographic data is in table 1. Mean pre-operative Uncorrected Distance Visual Acuity (UDVA) was 0.71, corrected distance visual acuity (CDVA) was 1.06. Mean ablation depth was 56.3 µ (range 16-116 µ) in the periphery of the ablation zone, and 3.65 µ centrally (range 2-23 µ).

At 3 months in 39 eyes post-operative mean spherical equivalent refraction (Se) was -0.05D + 0.27 D (range -1.00D to +0.63 D). Mean UDVA was 1.12, and mean CDVA was 1.18. efficacy was 1.06 and safety was 1.11. (Table 1) At 6 months post-operatively

table 1: Demographic data of the treatment groups

lasik lasek

# patients* 20 14

Male / female 12 male / 8 female 4 male / 10 female

# eyes 39 eyes 26 eyes

Age (range) 47.2 years (33-60) 51.1 years (31-59)

Mean pre-operative spherical equivalent refraction (range)

+1.88 D (+0.5 D to +4.25D)

+2.16 D (+0.75 D to +4.75 D)

Mean pre-operative cylinder (range) -0.68 D (0 to -4.75 D)

-0.8 D (0 to -4.00D)

Mean post-operative UDVA at 3 months

1.12 (20/18) 0.99 (20/20)

* Total 33 patients, because 1 patient had LASIK in OD and LASeK in OS due to flap cutting problems.

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in 19 eyes the mean Se was +0.04D + 0.24 D (range -1.00 to +0.75). Mean UDVA was 1.10 and mean CDVA was 1.19. efficacy was 1.04 and safety was 1.13.

In the LASEK group:Twenty six eyes of 14 patients had LASeK. Again the demographic data is shown in table 1. Mean pre-operative UDVA was 0.45, while CDVA was 1.04. Mean ablation depth was 57.79 (range 23-119) micron peripherally, and 3.8 micron centrally (range 2-20 micron).

At 3 months in 26 eyes post-operative Se was +0.15 D + 0.11 D (range -0.25 to +1.25D). Mean UDVA was 0.99 and mean CDVA was 1.07. efficacy was 0.95 and safety 1.03. (see table 1) At 6 months follow up data are available on 20 eyes: mean Se is +0.08D + 0.32 D ( range -0.875 to +1.25 D). Mean UDVA 1.0 and CDVA is 1.02. efficacy is 0.96 and safety is 0.98.

For both LASIK and LASeK groups the lines gained or lost at 3 months are summarized in figure 1.

The difference in postoperative UDVA and CDVA between the LASIK and LASeK group was statistically significant (Students t-test, 1-tailed, unequal variance, p = 0.03).

straylight outcomesPre-operatively straylight was found to be increased by 0.005 log units (not statistically significant, p>0.05) compared to the normal population17. In LASIK straylight increased 3 months post-operatively by log (s) 0.051 + 0.158. This increase was statistically not significant (p>0.05). In 50% of eyes the straylight values increased, and in 50% of eyes the straylight values decreased. (Figure 2) In the LASeK group the straylight increased on average by 0.031 log (s) + 0.146. This was also not statistically significant (p>0.05). Here in 54 % of eyes the straylight values increased, while in 46% of eyes the straylight values decreased (improved). (Figure 3)

5 Straylight Before and After Hyperopic LASIK and LASEK.

119

( range -0.875 to +1.25 D). Mean UDVA 1.0 and CDVA is 1.02. Efficacy is 0.96 and safety

is 0.98.

For both LASIK and LASEK groups the lines gained or lost at 3 months are summarized in

figure 1.

The difference in postoperative UDVA and CDVA between the LASIK and LASEK group

was statistically significant (Students t-test, 1-tailed, unequal variance, p = 0.03).

Lines gained or lost

3.82.6

34.6

11.5

34.6

15.5

30.1

7.7

33.3

25.6

0.05.010.015.020.025.030.035.040.0

-2 -1 0 1 2

Lines gained or lost

% e

yes

LASEKLASIK

Figure 1: In this figure we show the percentages of eyes that lost or gained lines from

pre-operative CDVA to post-operative UDVA. Most of the patients that lost lines were

due to undercorrections. In 1 eye in the LASEK group significant haze was thought to be

the cause of loss of lines. In all but 1 eye, these lines were regained on re-treatment.

Straylight outcomes:

Pre-operatively straylight was found to be increased by 0.005 log units (not statistically

significant, p>0.05) compared to the normal population17. In LASIK straylight increased 3

months post-operatively by log (s) 0.051 + 0.158. This increase was statistically not

significant (p>0.05). In 50% of eyes the straylight values increased, and in 50% of eyes

the straylight values decreased. (Figure 2) In the LASEK group the straylight increased on

average by 0.031 log (s) + 0.146. This was also not statistically significant (p>0.05). Here

figure 1: In this figure we show the percentages of eyes that lost or gained lines from pre-operative CDVA to post-operative UDVA. Most of the patients that lost lines were due to undercorrections. In 1 eye in the LASEK group significant haze was thought to be the cause of loss of lines. In all but 1 eye, these lines were regained on re-treatment.

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5 Straylight Before and After Hyperopic LASIK and LASEK.

120

in 54 % of eyes the straylight values increased, while in 46% of eyes the straylight values

decreased (improved). (Figure 3)

0.40

0.70

1.00

1.30

1.60


Post

-op

stra

ylig

ht le

vel

(log

(s))

Figure 2: The graph shows the comparison between the post- and pre-operative

straylight levels in hyperopic LASIK. The diagonal lines are the y=x line + 0.20 log units.

The error bars correspond with 0.05 log units, as these data points are averages over 2

measurements with a repeated measure SD of 0.07 log units. The mean straylight values

are increased by 0.051 log (s) postoperatively. This is not statistically significant, but

there are some individual cases with significant increase. 5 Straylight Before and After Hyperopic LASIK and LASEK.

121

0.40

0.70

1.00

1.30

1.60

0.4 0.7 1 1.3 1.6


Post

-op

stra

ylig

ht le

vel

(log

(s))

Figure 3: This graph shows the comparison between post and pre-operative straylight

values in hyperopic LASEK procedures. The diagonal lines are the y=x line + 0.20 log

units. The error bars correspond with 0.05 log units, as these data points are averages

over 2 measurements with a repeated measure SD of 0.07 log units. The mean post-

operative straylight is increased by 0.031. This is not statistically significant, but can be

clinically significant in individual cases.

Correlation of straylight outcomes to clinical and other parameters:

Pupil size:

The mean mesopic pupil was 3.7 mm in diameter (range 2.2 to 5.8 mm). The mean

scotopic pupil was 6.03 mm in diameter (range 3.5 to 7.9 mm). The mean optical zone

chosen for treatment was +2.75 mm wider than the mesopic pupil (range +0.7 mm to

+4.3 mm) and on average +0.42 mm wider than the scotopic pupil (range -0.9 mm to

+2.7 mm). On average the site of deepest ablation was at a a diameter of 9.8 mm, which

figure 2: The graph shows the comparison between the post- and pre-operative straylight levels in hyperopic LASIK. The diagonal lines are the y=x line + 0.20 log units. The error bars correspond with 0.05 log units, as these data points are averages over 2 measurements with a repeated measure SD of 0.07 log units. The mean straylight values are increased by 0.051 log (s) postoperatively. This is not statistically significant, but there are some individual cases with significant increase.

figure 3: This graph shows the comparison between post and pre-operative straylight values in hyperopic LASEK procedures. The diagonal lines are the y=x line + 0.20 log units. The error bars correspond with 0.05 log units, as these data points are averages over 2 measurements with a repeated measure SD of 0.07 log units. The mean post-operative straylight is increased by 0.031. This is not statistically significant, but can be clinically significant in individual cases.

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correlation of straylight outcomes to clinical and other parameters

Pupil sizeThe mean mesopic pupil was 3.7 mm in diameter (range 2.2 to 5.8 mm). The mean scotopic pupil was 6.03 mm in diameter (range 3.5 to 7.9 mm). The mean optical zone chosen for treatment was +2.75 mm wider than the mesopic pupil (range +0.7 mm to +4.3 mm) and on average +0.42 mm wider than the scotopic pupil (range -0.9 mm to +2.7 mm). On average the site of deepest ablation was at a a diameter of 9.8 mm, which is the sum of mean mesopic pupil of 3.7 mm and the optical zone of +2.75mm, and the maximal ablation being 3.3 mm in diameter beyond the optical zone diameter. This is well beyond the mesopic as well as scotopic pupil size in all cases.

Clinical findings such as haze, flap striae, and interface debrisIn LASIK in 8 eyes (5 patients) with > 0.20 log units increased straylight levels interface debris was found in the flap interface in 3 eyes of 3 patients. Of these, 2 patients had complaints on visual quality. The other 3 patients (5 eyes) were satisfied with the quality of vision. The interface debris was mostly central in the interlamellar space. So, central interface debris seems to be a cause for increased straylight, but is not always correlated to visual complaints in our patients.

No flap striae were seen in any of the eyes. Interface debris was seen in 1 other eye with a log (s) change <0.2, not resulting in clinical complaints.

In LASeK in 4 eyes of 3 patients in which straylight values were > 0.20 log units increased, haze could be seen in 3 eyes. Two of these patients (3 eyes), were dissatisfied with their quality of vision. In 2 eyes of 2 other patients haze grade 1 was seen, with log (s) change <0.2. Both patients had no complaints as to their visual acuity or quality of vision. In all of these eyes the haze was midperipheral at the zone of deepest ablation, and peripheral to the mesopic pupil opening.

repeatability of the measurementsAlthough the test employed in the C-Quant (“compensation comparison” paradigm) is designed in such a way that subject bias is impossible, it was considered prudent to check whether a learning effect might be possible. For this purpose in our studies first measurements are repeated, and a comparison is made of second to the first measurements. Moreover such data provide an independent measure of repeatability, to be compared to the eSD values given by the C-quant instrument. Overall, the mean difference was 0.008 log units, and repeated measures standard deviation was 0.078 log units.10 So, no learning process exists that may upset the sequential comparison.

discussion

In an earlier study we conducted in myopic treatments 10 we surprisingly found that straylight is as a rule decreased after surgery, except in a few cases, in which we could usually correlate the increase in straylight to findings in the cornea like haze, interface debris or flap striae. A correlation between straylight change and ablation depth was

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found, suggesting that a thinner central cornea is beneficial for straylight, although the effect may be very small. As a test for this explanation, the hyperopic group is interesting. Indeed at 3 months post-operatively straylight is on average increased by 0.051 and 0.031 log units respectively in LASIK and LASeK treatments. This increase is statistically and clinically not significant. However, in every population where the mean change is small or not significant for the whole group, individuals may still have an individually significant change from the baseline for which we try to find a clinical explanation.

The ablation profile in hyperopic treatments removes most tissue peripheral to the mesopic pupil opening. Issues like haze, interface debris, and flap striae may be assumed to play the same role in hyperopic treatments as in myopic LASIK and LASeK. 10, 11 The difference between the two treatments is in the location with respect to the pupil center. In the myopes we found a decrease in straylight, and this effect was related to ablation depth and thinning of the cornea. In hyperopes we found a small and statistically and clinically insignificant increase in straylight, most probably because of the more peripheral ablation of tissue. This finding is consistent with our previous findings, and contrary to our expectation of glare disability being increased after corneal excimer laser surgery.

In the Planoscan nomogram hyperopic ablation profile, the maximal ablation occurs 1.67 mm peripheral to the chosen treatment zone, which is chosen at least 0.7 mm peripheral to the mesopic pupil opening. Tissue changes centrally in the pupillary zone are minimal, and this may be one reason for the lack of change, in most cases after hyperopic treatment. The central area of the cornea, in the pupillary opening, is the area that contributes most in straylight from corneal sources.18

In our myopic population we have found that the baseline straylight measurement was significantly increased by 0.06 log units. This relative elevation disappeared upon surgery. Also Rozema and colleagues19 reported straylight elevation in myopes. When trying to explain this phenomenon, contact lens wear must be considered. Reports of contact lens effects on straylight have shown strong results, sometimes including long-term effects, but also variable [review in van der Meulen et al. 17]. Our patients were instructed not to wear contact lenses at least 72 hours before the measurement in soft contact lenses, and 4-16 weeks in hard contact lenses. In the present study pre-operatively the straylight values are not significantly increased by 0.005 log units compared to the normal population. Although unlikely, we would not like to rule out the possibility that contact lens use could be on the basis of the difference in baseline measurements between the hyperopes and the myopes. Another issue to be considered is axial length. In myopic eyes light has to travel a longer distance, with potentially more scattering elements. However, this is inconsistent with the reduction upon treatment in myopes. Another effect we explored was pre-operative pachymetry. However there was no significant difference. The mean pachymetry in the hyperopes (thinnest point on the Orbscan) was 539µ, and 530µ in our myopic population (t-test, 2-tailed, p=0.09).

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From the literature hyperopic corneal refractive surgery had always lagged in outcomes, compared to myopic treatments. The consensus has been that hyperopic corrections until 4 diopters are safer and more predictable than the higher corrections.20 Hyperopic treatments have higher rates of regression, but in some instances latent hyperopia may play a role in undercorrection. The hyperopic excimer laser ablation pattern tries to steepen the cornea in the mid-periphery, which is more difficult to achieve12-15. Stromal regrowth and epithelial hyperplasia play a role in these processes. 21 These same processes can be expected to play a role in straylight. In cases of haze and interlamellar debris are particles visible on slitlamp, that probably cause increased straylight in some instances.10, 11 Also in instances of epithelial ingrowth we have shown that ingrowth over the pupillary opening has much more impact on straylight, than ingrowth that does not reach the pupillary opening. 22

Clinically there was a correlation between increased straylight and findings in the cornea, like haze and interlamellar debris, but the numbers of these adverse events are low. These findings are often correlated with patients’ dissatisfaction with their vision. In some of the eyes in which straylight was increased, we could clinically find a correlation in the cornea in the form of interface debris in LASIK and haze in LASeK. However, in the group as a whole, the mean increase in straylight is minimal and clinically not significant. We did not specifically administer a questionnaire on glare related issues, which needs to be implemented in our future studies. Also the contribution of tearfilm changes in our population, to complaints of visual dissatisfaction in the outcomes was not researched. In the literature the change in the tearfilm is generally accepted as a reason for decreased visual quality and dissatisfaction with visual quality. 23, 24

There is no definite evidence based answer to whether LASIK or LASeK is the better treatment of hyperopia. 25 Surface ablations are associated with more post-operative pain, slower visual recovery, and corneal haze. Our visual acuity outcomes are comparable to what has previously been published.20, 26, 27 el Agha found that nearly 20% of patients who had hyperopic PRK had midperipheral haze.26,27

This is comparable to our finding haze in 5 of 26 eyes. Only 3 out of these 5 eyes had post-operatively increased straylight measurements as compared to their pre-operative straylight. This is explained by the fact that the haze is concentrated in the area with the deepest ablation, which is the peripheral cornea, approximately 2 mm from the mesopic pupil.

in conclusion

In hyperopic LASIK and LASeK straylight levels increase slightly on average postoperatively. This increase is not statistically significant, but in a small percentage of individual cases clinically significant changes may occur. This is consistent with our findings in myopic laser treatments, were there is a small decrease in straylight post-operatively. In some eyes the increase of straylight could be related to findings in the cornea. The reason for the increase could be related with tissue changes, but this has to be studied in more detail.

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references

1. Vos JJ. Disability glare - state of the art re-port. Commission International d’eclairage Journal 1984;3(2):39-53.

2. Cervino A, Montes-Mico R, Hosking SL. Performance of the compensation com-parison method for retinal straylight measurement: effect of patient’s age on repeatability. The British journal of oph-thalmology 2008;92(6):788-91.

3. van den Berg T, Franssen, L, Coppens, J.e. Straylight in the human eye: testing objec-tiivity and optical character of the psycho-physical measurements. Ophthalm Physiol Opt 2009;29(1):1-6.

4. van den Berg TJ. On the relation between glare and straylight. Doc Ophthalmol 1991;78(3-4):177-81.

5. van den Berg TJ. Analysis of intraocular straylight, especially in relation to age. Op-tom Vis Sci 1995;72(2):52-9.

6. Chang SW, Benson A, Azar DT. Corneal light scattering with stromal reformation af-ter laser in situ keratomileusis and photore-fractive keratectomy. Journal of cataract and refractive surgery 1998;24(8):1064-9.

7. Jain S, Khoury JM, Chamon W, Azar DT. Corneal light scattering after laser in situ keratomileusis and photorefractive kerate-ctomy. American journal of ophthalmology 1995;120(4):532-4.

8. Jain S, McCally RL, Connolly PJ, Azar DT. Mitomycin C reduces corneal light scat-tering after excimer keratectomy. Cornea 2001;20(1):45-9.

9. Kim TI, Pak JH, Lee SY, Tchah H. Mitomycin C-induced reduction of keratocytes and fi-broblasts after photorefractive keratecto-my. Investigative ophthalmology & visual science 2004;45(9):2978-84.

10. Lapid-Gortzak R. vdLJW, van der Meulen I.J.e., Nieuwendaal C.P., Mourits M.P., and van den Berg T.J.T.P. Straylight measure-ment in myopic LASIK and LASeK. Journal Cataract Refract Surgery in press.

11. Beerthuizen JJ, Franssen L, Landesz M, van den Berg TJ. Straylight values 1 month after laser in situ keratomileusis and photorefrac-tive keratectomy. Journal of cataract and re-fractive surgery 2007;33(5):779-83.

12. McGhee CN, Ormonde S, Kohnen T, Law-less M, Brahma A, Comaish I. The surgical correction of moderate hypermetropia: the

management controversy. The British jour-nal of ophthalmology 2002;86(7):815-22.

13. Azar DT, Primack JD. Theoretical analysis of ablation depths and profiles in laser in situ keratomileusis for compound hyperopic and mixed astigmatism. Journal of cataract and refractive surgery 2000;26(8):1123-36.

14. Primack JD, Azar DT. Refractive surgery for hyperopia. International ophthalmology clinics 2000;40(3):151-63.

15. Sher NA. Hyperopic refractive sur-gery. Current opinion in ophthalmology 2001;12(4):304-8.

16. Coppens Je, Franssen L, van den Berg TJ. Reliability of the compensation com-parison method for measuring retinal stray light studied using Monte-Carlo simula-tions. J Biomed Opt 2006;11(5):054010.

17. van der Meulen IJe eL, van Vliet JMJ, La-pid-Gortzak R, Nieuwendaal CP, Mourits MP, Schlingemann RO, van den Berg TJTP. Straylight measuerements in contact lens wear. Cornea in press.

18. Franssen L, Tabernero J, Coppens Je, van den Berg TJ. Pupil size and retinal straylight in the normal eye. Investigative ophthal-mology & visual science 2007;48(5):2375-82.

19. Rozema JJ, Van den Berg TJ, Tassignon MJ. Retinal Straylight as a Function of Age and Ocular Biometry in Healthy eyes. In-vestigative ophthalmology & visual sci-ence 2009.

20. Corones F, Gobbi PG, Vigo L, Brancato R. Photorefractive keratectomy for hyper-opia: long-term nonlinear and vector anal-ysis of refractive outcome. Ophthalmology 1999;106(10):1976-82; discussion 82-3.

21. Dierick HG, Van Mellaert Ce, Missotten L. Histology of rabbit corneas after 10-diopt-er photorefractive keratectomy for hyper-opia. J Refract Surg 1999;15(4):459-68.

22. Lapid-Gortzak R, van der Meulen I, van der Linden JW, Nieuwendaal C, Mourits M, van den Berg T. Straylight measurements before and after removal of epithelial in-growth. Journal of cataract and refractive surgery 2009;35(10):1829-32.

23. Behrens A, Doyle JJ, Stern L, et al. Dys-functional tear syndrome: a Delphi ap-proach to treatment recommendations. Cornea 2006;25(8):900-7.

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24. Berry S, Mangione CM, Lindblad AS, McDonnell PJ. Development of the National eye Institute refractive er-ror correction quality of life question-naire: focus groups. Ophthalmology 2003;110(12):2285-91.

25. Settas G, Settas C, Minos e, Yeung IY. Pho-torefractive keratectomy (PRK) versus la-ser assisted in situ keratomileusis (LASIK) for hyperopia correction. Cochrane da-tabase of systematic reviews (Online) 2009(2):CD007112.

26. el-Agha MS, Bowman RW, Cavanagh D, McCulley JP. Comparison of photorefrac-tive keratectomy and laser in situ keratomi-leusis for the treatment of compound hyperopic astigmatism. Journal of cataract and refractive surgery 2003;29(5):900-7.

27. el-Agha MS, Johnston eW, Bowman RW, Cavanagh HD, McCulley JP. Pho-torefractive keratectomy versus laser in situ keratomileusis for the treatment of spherical hyperopia. eye & contact lens 2003;29(1):31-7.

STRAYLIGHT MeASUReMeNTS BeFORe AND AFTeR ReMOVAL

OF ePITHeLIAL INGROWTH

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abstract

In 3 eyes with epithelial ingrowth after laser in situ keratomileusis, straylight was measured before and after the ingrowth was removed. In 2 eyes of 1 patient, epithelial ingrowth reached the pupillary axis. Straylight decreased (improved) significantly after ingrowth removal: a 3.6-fold decrease in the right eye and a 10-fold decrease in the left eye. The uncorrected distance visual acuity (UDVA) improved from 0.25 (20/80) in both eyes to 1.0 (20/20) and 0.8 (20/25), respectively. In 1 eye of another patient, from which epithelial ingrowth was removed to prevent flap melting and distortion, the pupillary opening was not obscured and no significant change in straylight was found. The UDVA improved from 0.32 (20/60) to 1.0 (20/20) after the ingrowth was removed. An increase in straylight can be a significant complication of epithelial ingrowth. After the interlamellar space is cleared, the improvement in straylight is several factors larger than the gain in UDVA.

ruth lapid-gortzak1, 2, md, ivanka J.e. van der meulen1, 2, md, Jan Willem van der linden1, carla p. nieuwendaal2, md, maarten p. mourits2, md, phd, tom J.t.p. van den berg, phd3

1 Retina Total Eye Care, Driebergen, the Netherlands; 2 Department of Ophthalmology, Academic Medical Center, University of Amsterdam, the Netherlands; 3 Institute for Neuroscience, Royal Academy, Amsterdam, The Netherlands.

Journal Cataract and Refractive Surgery 2009; 35:1829–1832

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introduction

epithelial ingrowth is a well-known complication of lamellar corneal surgery. It occurs in 1% to 20% of laser in situ keratomileusis (LASIK) procedures.1,2 Most epithelial ingrowth is self-limited and has no or minimal consequences on visual acuity. In 1% to 1.7% of cases, it is more persistent and extensive and may reach the visual axis or lift the flap and cause irregular astigmatism and flap melting.1–3 Visual acuity is usually compromised in these cases. The ingrowth has to be surgically removed to preserve the corneal integrity and improve visual acuity.

Straylight corresponds to the light that enters the eye but does not reach the retina in a focused manner. It forms a veil of light that is scattered over the retina by intraocular structures such as the cornea, lens, iris, and other intraocular media.4 Straylight is a parameter of quality of vision. It describes disability glare from light sources. This parameter often correlates well with complaints about quality of vision after refractive surgery procedures, even if visual acuity is 1.0 (20/20) or better.5–7

The C-Quant straylight meter (Oculus Optikgeraete GmbH) measures straylight in an objective but functional manner.8 It provides direct information about optical imperfections as the cause of glare disability. Glare disability is the reduction in visual performance caused by a glare source, which causes retinal contrast degradation secondary to intraocular straylight. The most common example is an oncoming headlight as a glare source, causing a contrast loss that leads to the patient not able to see an object (such as a car) in front of her or him. The C-Quant determines straylight according to the internationally accepted definition (Commission Internationale d’eclairage [CIe]). Straylight is a functional measure of the effect of light spreading over the retina, introduced as the CIe definition for ‘‘disability glare.’’ The amount of straylight is expressed as straylight parameter s. We studied the effect of removing intralamellar epithelial ingrowth on quality of vision as determined by straylight values.4,6,9–12

figure 2. Case 1, left eye: At 6 months interface and flap edges are clean.

figure 1. Case 1, left eye: Preoperative image of the epithelial ingrowth shows encroachment on the pupil. The photograph is underexposed as the glare disability made it difficult for the patient to cooperate.

6 Straylight Measurements Before and After Removal of Epithelial Ingrowth

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Left Eye At presentation, the UDVA was 0.25 (20/80) and the CDVA was 0.63 (20/30) with a refraction of plano -3.00 x 60. Slitlamp examination showed a dense plaque of ingrowth in the interlamellar space of the LASIK flap. The ingrowth was dense and looked persistent, lacking the characteristic bubbly appearance of epithelial cysts. The ingrowth encroached on the visual axis (Figure 1). The extent and density of the ingrowth, which clearly caused the visual complaints, were the indications for removal. The ingrowth proved persistent. On postoperative day 3, the patient removed the bandage contact lens and rubbed her eye. This may have played a role in the recurrence that occurred subsequently. Two more procedures were needed to halt the process. Five months after the third procedure, the UDVA and CDVA had improved and the cornea was clear with a clear interface. At the interface, an ‘‘imprint’’ of where the ingrowth plaque had been could be discerned but no ingrowth was left (Figure 2). Straylight improved from preoperatively to 6 months, an improvement factor of 10. The 6-month value was within the normal range for this age. Right

Eye Left

Eye

Date UDVA CDVA Refraction Log(s) UDVA CDVA Refraction Log(s)

Intake . 0.25 0.63 Plano -2.00 x 145 1.82 0.25 0.63 Plano -3.0 x 60 2.05

Postop (mo)

3 0.8 0.8 Plano 1.36 0.8 0.8 Plano -0.50 x 6 1.57

6 1.0 1.0 Plano 1.26 0.8 0.8 Plano -0.50 x 6 1.06

Table 1: Case 1: Changes in visual acuity, refraction, and log (s) in both eyes from before epithelial ingrowth removal to 6 months postoperatively. CDVA = corrected distance visual acuity; UDVA = uncorrected distance visual acuity.

Figure 1. Case 1, left eye: Preoperative image Figure 2. Case 1, left eye: At 6 months of the epithelial ingrowth shows encroachment interface and flap edges are clean. on the pupil. The photograph is underexposed as the glare disability made it difficult for the patient to cooperate.

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Left Eye At presentation, the UDVA was 0.25 (20/80) and the CDVA was 0.63 (20/30) with a refraction of plano -3.00 x 60. Slitlamp examination showed a dense plaque of ingrowth in the interlamellar space of the LASIK flap. The ingrowth was dense and looked persistent, lacking the characteristic bubbly appearance of epithelial cysts. The ingrowth encroached on the visual axis (Figure 1). The extent and density of the ingrowth, which clearly caused the visual complaints, were the indications for removal. The ingrowth proved persistent. On postoperative day 3, the patient removed the bandage contact lens and rubbed her eye. This may have played a role in the recurrence that occurred subsequently. Two more procedures were needed to halt the process. Five months after the third procedure, the UDVA and CDVA had improved and the cornea was clear with a clear interface. At the interface, an ‘‘imprint’’ of where the ingrowth plaque had been could be discerned but no ingrowth was left (Figure 2). Straylight improved from preoperatively to 6 months, an improvement factor of 10. The 6-month value was within the normal range for this age. Right

Eye Left

Eye

Date UDVA CDVA Refraction Log(s) UDVA CDVA Refraction Log(s)

Intake . 0.25 0.63 Plano -2.00 x 145 1.82 0.25 0.63 Plano -3.0 x 60 2.05

Postop (mo)

3 0.8 0.8 Plano 1.36 0.8 0.8 Plano -0.50 x 6 1.57

6 1.0 1.0 Plano 1.26 0.8 0.8 Plano -0.50 x 6 1.06

Table 1: Case 1: Changes in visual acuity, refraction, and log (s) in both eyes from before epithelial ingrowth removal to 6 months postoperatively. CDVA = corrected distance visual acuity; UDVA = uncorrected distance visual acuity.

Figure 1. Case 1, left eye: Preoperative image Figure 2. Case 1, left eye: At 6 months of the epithelial ingrowth shows encroachment interface and flap edges are clean. on the pupil. The photograph is underexposed as the glare disability made it difficult for the patient to cooperate.

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methods

In this prospective case series of 3 treated eyes, the tenets of the Helsinki Agreement were adhered to. After informed consent was given, the clinically significant epithelial ingrowth in post-LASIK eyes were treated. Topical anesthesia was applied using oxybupivacaine and tetracaine eyedrops 3 times at 5-minute intervals. The eyes were swabbed with povidone–iodine 5% solution, which was also instilled in the fornices for 2 minutes. The eyes and lashes were draped with tape. Using a blunt instrument, the epithelium was removed 2.0mm from the central and peripheral edge of the LASIK flap to 2.0mm beyond the edge of the ingrowth radially. The flap was then lifted with a blunt forceps. The epithelial ingrowth was removed in one movement from the stromal bed or the underside of the LASIK flap using a forceps. Remnants were identified and removed. Alcohol 20% was applied to the stromal interlamellar surface, which was then rinsed with balanced salt solution (BSS).

The LASIK flap was irrigated and replaced, and the flap edges were replaced using slight pressure from Weck-Cel spears (Medtronic Xomed, Inc.). The flap was allowed to adhere for 2 to 3 minutes while BSS drops were instilled on top of the flap. Fibrin glue was then applied at the flap edge, covering the central and peripheral flap edge. The glue was allowed to dry for several minutes. The extent of the glue was checked with a spear; where necessary, excess glue was removed with a Vannas scissors. A bandage soft contact lens soaked in gentamicin 0.4% was placed on the cornea.

Postoperatively, the patients received preservative-free chloramphenicol 0.4% and prednisolone 0.5% eyedrops hourly for the first 24 hours and an oral analgesic agent. The drops were tapered over subsequent days. The bandage contact lens was removed on postoperative day 7 in both cases.

Straylight was measured in undilated pupils with the C-Quant straylight meter as part of the perioperative protocol. Internal quality parameters of reliability expected standard deviation and quality had to be lower than 0.08 and higher than 0.5, respectively.

case reports

case 1A 52-year-old woman presented with complaints of gradual visual loss and foreign-body sensation in both eyes. She had had LASIK for myopia in the Dominican Republic 3 years previously but could not provide the preoperative and postoperative refractions and visual acuity measurements.

Right EyeAt presentation, the uncorrected distance visual acuity (UDVA) was 0.25 (20/80) and the corrected distance visual acuity (CDVA) was 0.63 (20/30) with a refraction of plano –-2.00 x 145. Slitlamp examination revealed epithelial ingrowth laterally in the flap with a communicating channel that was visible with fluorescein staining. Otherwise,

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the ocular examination was normal. A decision to remove the epithelial ingrowth was made because of the complaint of visual loss and the communication with the interlamellar space, although this was not extensive. One procedure sufficed. The UDVA and CDVA gradually improved, with clear corneal flaps and no recurrence of the ingrowth after 10 weeks (Table 1). Straylight was very high at intake but improved after epithelial removal (Table 1); at 6 months, the improvement factor was 3.6. The 6-month value was slightly higher than normal levels for the patient’s age.

table 1: Case 1: Changes in visual acuity, refraction, and log (s) in both eyes from before epithelial ingrowth removal to 6 months postoperatively.

date

right eye left eye

udVa cdVa refraction log(s) udVa cdVa refraction log(s)

Intake . 0.25 0.63 Plano -2.00 x 145 1.82 . 0.25 0.63 Plano -3.0 x 60 2.05

Postop (mo)

3 0.8 0.8 Plano 1.36 0.8 0.8 Plano -0.50 x 6 1.57

6 1.0 1.0 Plano 1.26 0.8 0.8 Plano -0.50 x 6 1.06

CDVA = corrected distance visual acuity; UDVA = uncorrected distance visual acuity.

Left EyeAt presentation, the UDVA was 0.25 (20/80) and the CDVA was 0.63 (20/30) with a refraction of plano -3.00 x 60. Slitlamp examination showed a dense plaque of ingrowth in the interlamellar space of the LASIK flap. The ingrowth was dense and looked persistent, lacking the characteristic bubbly appearance of epithelial cysts. The ingrowth encroached on the visual axis (Figure 1). The extent and density of the ingrowth, which clearly caused the visual complaints, were the indications for removal. The ingrowth proved persistent. On postoperative day 3, the patient removed the bandage contact lens and rubbed her eye. This may have played a role in the recurrence that occurred subsequently. Two more procedures were needed to halt the process. Five months after the third procedure, the UDVA and CDVA had improved and the cornea was clear with a clear interface. At the interface, an ‘‘imprint’’ of where the ingrowth plaque had been could be discerned but no ingrowth was left (Figure 2). Straylight improved from preoperatively to 6 months, an improvement factor of 10. The 6-month value was within the normal range for this age.

case 2A 48-year-old woman presented with a residual refractive error after LASIK for myopia of -3.50 -1.00 x 130 in the right eye in 2002. Regression had stabilized at a UDVA of 0.4 (20/55) and a CDVA of 1.0 (20/20) with a correction of -1.25 -0.75 x 179. The flap in the right eye was lifted and an ablation performed for the above correction. One day postoperatively, the UDVA was 0.8 (20/25); at 1 week, it was 1.0 (20/20) and

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the CDVA was 1.25 (20/15) with a correction of +0.75 -0.50 x 20. At 1 month, the patient complained of worse vision. The UDVA was 0.32 (20/60), and the CDVA was 1.3 (20/17) with a refraction of +1.75 sphere. epithelial ingrowth up to 2.0 mm from the periphery of the flap and flap striae were seen at the inferior aspect of the flap. The epithelial ingrowth was removed because of progression, decreased UDVA, and the onset of flap melting peripherally. The pupillary axis and its overlying cornea were not affected. The surgical procedure was identical to that described.

Postoperatively, visual acuity improved gradually (Table 2). The patient is satisfied with the result in the right eye. Although the myopic LASIK treatment in the left eye also regressed, she is happy with monovision. The refraction in the left eye is -1.25-0.5x 174 with a CDVA of 1.0 (20/20); the uncorrected near visual acuity is 1.0 (20/20). Straylight measurement was repeated once at each examination. Table 2 shows the log(s) values before retreatment of the residual myopia, immediately before epithelial ingrowth removal, and 6 weeks and 5 months after ingrowth removal.

table 2: Case 2: Change in visual acuity, refraction, and log (s) from before the enhancement procedure to 5 months after epithelial ingrowth removal.

date udVa cdVa refraction log(s)

Before enhancement 0.4 1.0 +1.25-0.75x180 0.850.92

Before Removal 0.32 1.3 +1.75 1.13

Postop:

6 weeks 0.9 - - 1.131.18

5 months 1.0 1.1 +0.75 1.091.09

CDVA = corrected distance visual acuity; UDVA = uncorrected distance visual acuity

discussion

epithelial ingrowth is a phenomenon encountered in 1% to 20% of LASIK procedures. Most lesions are self-limited and may disappear with time. Some need surgical intervention. The indications for surgical intervention are a communicating channel that persists (a fistula), melting of the LASIK flap, irregular astigmatism with loss of visual acuity, and obscuration of the visual axis.2,3 In the 3 eyes presented, removal of epithelial ingrowth improved UDVA significantly and CDVA to a small extent. Straylight behaved quite differently. In the 2 eyes with ingrowth reaching the pupillary axis (Case 1), straylight increased significantly. When it is compared with the normal values at 50 years of age of about log(s) =1.0, the increase is close to a factor of 10.5 This a very disabling level. Straylight was significantly reduced after the interface was cleaned by physically removing the epithelial ingrowth. The epithelial ingrowth with

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its secondary local changes impedes the proper passage of light through the cornea and increases straylight. Clearing the media, in this case the cornea, contributed to a reduction (ie, improvement) in straylight that was greater than the improvement in Snellen visual acuity. This difference between straylight and visual acuity has also been reported for age-related changes in the crystalline lens.5 However, the opposite can also be observed in the aging crystalline lens.5 The relative independence of these 2 functional aspects of vision in relation to media changes can be partly understood on the basis of the underlying optics of the ocular media.5,8 Changes of a refractile nature (aberrations) influence visual acuity but not straylight. Small irregularities (order of magnitude in the micron range) influence straylight but not visual acuity.

The eye in Case 2 illustrates the opposite effect. We did not see much change in straylight with the onset or removal of the epithelial ingrowth, the plausible explanation being that the indication for removal of the ingrowth was keratolysis, melting of the flap edges. The central part of the cornea was not covered by ingrowth. Analysis and statistical testing (repeated measures analysis of variance) showed significant difference between the sessions (P= .003). However, the repeated measures standard deviation that can be calculated for this patient from the dataset is exceptionally good (0.03 log units) compared with published values (around 0.07 log units).5,13 Also, given the normal spreading within the population of 0.1 log units, the differences between the sessions are limited.5 This means the minimal changes in straylight are real and not significant.

Straylight is a parameter of visual quality. It is usually not increased after LASIK procedures.14,15 In this case series, we show that central epithelial ingrowth may increase straylight to highly disabling levels. Its removal decreases straylight values to values comparable to those in the rest of the population. The straylight values were reproducible with repeated measuring. In conclusion, straylight is an important functional measure to consider when evaluating epithelial ingrowth. More study is needed to delineate the cause and effect relationships between epithelial ingrowth, flap surface irregularity, and straylight. Currently, clearing the interface and a more normal adherent fit of the LASIK flap to the residual stromal bed seem to be effective in reducing straylight values.

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1. Jun RM, Cristol SM, Kim MJ, KYul Seo, Kim JB, Kim eK. Rates of epithelial ingrowth after LASIK for different excimer laser sys-tems. J Refract Surg 2005; 21:276–280

2. Latkany RA, Haq Fe, Speaker MG. Ad-vanced epithelial ingrowth 6 months after laser in situ keratomileusis. J Cataract Re-fract Surg 2004; 30:929–931

3. Jabbur NS, Chicani CF, Kuo IC, O’Brien TP. Risk factors in interface epithelialization after laser in situ keratomileusis. J Refract Surg 2004; 20:343–348

4. Vos JJ. Disability glare – a state of the art report. CIe J 1984;3(2):39–53

5. van den Berg TJTP, van Rijn LJ, Michael R, Heine C, Coeckelbergh T, Nischler C, Wil-helm H, Grabner G, emesz M,

6. Barraquer RI, Coppens Je, Franssen L. Straylight effects with aging and lens extraction. Am J Ophthalmol 2007; 144:358–363

7. van den Berg TJTP. On the relation be-tween glare and straylight. Doc Ophthal-mol 1991; 78:177–181

8. van den Berg TJTP. Analysis of intraocular straylight, especially in relation to age. Op-tom Vis Sci 1995; 72:52–59

9. van den Berg TJTP, Franssen L, Coppens Je. Straylight in the human eye: testing ob-jectivity and optical character of the psy-chophysical measurement. Ophthalmic Physiol Opt 2009; 29:345–350

10. Coppens Je, Franssen L, van den Berg TJTP. Wavelength dependence of in-

traocular straylight. exp eye Res 2006; 82:688–692

11. Coppens Je, Franssen L, van den Berg TJTP. Reliability of the compensation comparison method for measuring retinal straylight studied using Monte-Carlo simu-lations. J Biomed Opt 2006; 11:054010

12. Franssen L, Coppens Je, van den Berg TJTP. Compensation comparison method for assessment of retinal straylight. Invest

13. Ophthalmol Vis Sci 2006; 47:768–776. Available at: http://www.iovs.org/cgi/re-print/47/2/768. Accessed June 11, 2009

14. Franssen L, Tabernero J, Coppens Je, van den Berg TJTP. Pupil size and reti-nal straylight in the normal eye. Invest Ophthalmol Vis Sci 2007; 48:2375–2382. Available at: http://www.iovs.org/cgi/re-print/48/5/2375. Accessed June 11, 2009

15. Cerviño A, Montes-Mico, Hosking SL. Per-formance of the compensation comparison method for retinal straylight measurement: effect of patient’s age on repeatability. Br J Ophthalmol 2008; 92:788–791

16. Beerthuizen JJG, Franssen L, Landesz M, van den Berg TJTP. Straylight values 1month after laser in situ keratomileusis and photorefractive keratectomy. JCata-ractRefractSurg2007; 33:779–783

17. Schallhorn SC, Blanton CL, Kaupp Se, Sut-phin J, Gordon M, Goforth H Jr, Butler FK Jr. Preliminary results of photorefractive keratectomy in active-duty United States Navy personnel. Ophthalmology 1996; 103:5–21; discussion by LJ Maguire, 21–22

references

HeRPeS SIMPLeX VIRUS KeRATITIS AFTeR LASeR IN SITU KeRATOMILeUSIS

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abstract

purpose: To report two cases of herpes simplex virus (HSV) keratitis after laser in situ keratomileusis (LASIK).

methods: Interventional small case series. Two patients underwent uneventful LASIK. History of herpes labialis in one patient and herpetic eye disease 10 years prior to intervention in the other patient was reported. Both patients developed stromal herpetic keratitis 6 weeks and 2 years after the procedure, respectively.

results: Treatment consisting of topical steroid drops and topical and systemic antiviral therapy was administered. Recurrences of the herpetic keratitis were seen after tapering of the topical steroids; four and three recurrences were observed, respectively. Final visual acuity was 6/9 in both cases.

conclusions: Herpetic keratitis after LASIK is an uncommon, possibly under-reported, entity. even patients without history of herpetic eye disease can present with this complication. Oral antiviral prophylaxis may be appropriate when performing LASIK on patients with a history of ocular or systemic HSV infection.

Jaime levy, md, ruth lapid-gortzak, md, itamar klemperer, md, and tova lifshitz, md

From the Ophthalmology Department, Soroka University Medical Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel.

Journal of Refractive Surgery. 2005;21:400-402.

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Controversy exists regarding the potential triggers of recurrent ocular herpes simplex virus (HSV) disease,1 including upper respiratory tract infection, fever, seasonal conditions, and psychological stress. eye trauma, including refractive procedures, has also been proposed for this potential triggering effect.

In animal models, reactivation of latent HSV has been described following excimer laser photokeratectomy2,3 and laser in situ keratomileusis (LASIK).4 In humans, only three cases of reactivated HSV following LASIK have been reported previously.5-7

We present two cases of HSV keratitis following LASIK in two patients with previous herpes labialis and herpetic eye disease, respectively.

case reports

case 1A 32-year-old woman underwent bilateral LASIK for myopia. Preoperative refraction was S -4.25 C-1.75x 13° in the right eye and S-4.25 C-1.50x 8° in the left eye.

Uncorrected visual acuity (UCVA) was 6/120 in both eyes. Best spectacle-corrected visual acuity was 6/6 in both eyes. Ocular history was positive for herpes labialis.

Slit-lamp examination of anterior and posterior segments was normal. Cornea was completely clear bilaterally.

Laser in situ keratomileusis was performed with the Nidek eC-5000 excimer laser (Nidek Technologies, Gamagori, Japan) after a nasally hinged 160-μm flap was made by the Nidek 2000-MK microkeratome with an 8.5-mm suction ring. The laser procedure was not performed in the left eye because buttonhole formation in the center of the flap.

One day postoperatively, UCVA was 6/15 in the right eye, and the flap was clear. Dexamethasone and chloramphenicol drops four times a day were started.

Six weeks after the procedure and while on dexamethasone drops twice daily, the patient reported reduced vision in her right eye. Uncorrected visual acuity was 6/24. Slit-lamp examination revealed edema of the inferior cornea and keratic precipitates on the endothelium (Fig). Significant irregular astigmatism was observed on corneal computerized keratopography. Steroid drops were prescribed eight times a day. Because slow improvement was observed, primary HSV disciform keratitis was not suspected and antiviral therapy was not started. One month later, epithelial dendrites appeared, and acyclovir ointment five times a day and acyclovir tablets 400 mg five times a day were started. Uncorrected visual acuity improved to 6/9, and only a minimal haze at corneal interface remained.

During 18-month follow-up, four recurrences of the disciform herpetic keratitis occurred, always related to tapering of the steroid drops, and responding well to topical therapy. During the attacks, UCVA decreased to 6/24 with irregular astigmatism, returning to 6/9 after resolution.

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case 2A 39-year-old woman underwent bilateral LASIK for myopia performed elsewhere. Two years after the procedure, she reported pain and reduced vision in the right eye. Uncorrected visual acuity was 6/120. Ocular history was positive for ocular herpes that occurred in her late teens, with quiescence thereafter. Ocular examination revealed corneal epithelial dendrites, stromal edema, and Descemet’s folds. Treatment consisting of valacyclovir tablets 500 mg three times a day, acyclovir ointment five times a day, and dexamethasone drops four times a day was started. Uncorrected visual acuity improved to 6/6, and only a minimal stromal haze was observed. Three recurrences of the herpetic stromal disease were observed, twice after tapering of the topical steroids drops and once after discontinuation of the oral valacyclovir. During reactivation, UCVA decreased to counting fingers with remarkable recovery in between attacks. At present, 2 years after the first HSV recurrence, UCVA remains 6/6. During the past 10 months, the patient has not received any topical or systemic treatment.

figure. case 1. Right eye 6 weeks after LASIK showing edema of the inferior cornea and keratic precipitates on the endothelium. Uncorrected visual acuity is 6/24.

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Laser in situ keratomileusis was performed with the Nidek EC-5000 excimer laser (Nidek Technologies, Gamagori, Japan) after a nasally hinged 160-μm flap was made by the Nidek 2000-MK microkeratome with an 8.5-mm suction ring. The laser procedure was not performed in the left eye because buttonhole formation in the center of the flap. One day postoperatively, UCVA was 6/15 in the right eye, and the flap was clear. Dexamethasone and chloramphenicol drops four times a day were started. Six weeks after the procedure and while on dexamethasone drops twice daily, the patient reported reduced vision in her right eye. Uncorrected visual acuity was 6/24. Slit-lamp examination revealed edema of the inferior cornea and keratic precipitates on the endothelium (Fig). Significant irregular astigmatism was observed on corneal computerized keratopography. Steroid drops were prescribed eight times a day. Because slow improvement was observed, primary HSV disciform keratitis was not suspected and antiviral therapy was not started. One month later, epithelial dendrites appeared, and acyclovir ointment five times a day and acyclovir tablets 400 mg five times a day were started. Uncorrected visual acuity improved to 6/9, and only a minimal haze at corneal interface remained.

Figure. Case 1. Right eye 6 weeks after LASIK showing edema of the inferior cornea and keratic precipitates on the endothelium. Uncorrected visual acuity is 6/24. During 18-month follow-up, four recurrences of the disciform herpetic keratitis occurred, always related to tapering of the steroid drops, and responding well to topical therapy. During the attacks, UCVA decreased to 6/24 with irregular astigmatism, returning to 6/9 after resolution.

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discussion

each year an estimated 48,000 cases of active HSV eye disease present in the United States, and hundreds of thousands LASIK procedures are performed annually. Therefore, a larger number of cases of recurrent HSV disease after LASIK would be expected to occur than previously reported.5-7 Furthermore, inactive herpetic eye disease is not considered an absolute contraindication for refractive procedures. Although LASIK is theoretically less traumatic to the corneal epithelium than surface photorefractive keratectomy, both procedures have been demonstrated to reactivate HSV in a rabbit latency model.3 It has been suggested, based on results on this same model,8 that patients with a history of recurrent ocular herpes may be able to safely undergo LASIK with less risk of a recurrent herpetic episode while on valacyclovir antiviral prophylaxis, although authors noted that controlled clinical trials have yet to be performed. The Herpetic eye Disease Study Group did not find relationships between psychological stress, systemic infection, sunlight exposure, menstrual period, contact lens wear or eye injury, and recurrence of ocular HSV disease. In the three previously reported cases, and in our present two cases, the trigger for the recurrence of ocular HSV disease is unclear. It is difficult to ascertain whether the LASIK procedure played a role. We can only suggest a temporal relationship between LASIK procedure and ocular HSV reactivation. In reported cases, presentation occurred between 1 day and 2 weeks after the procedure.5-7 Two patients had previous ocular HSV disease,5,7 and one patient had herpes labialis.6 Prophylactic oral famciclovir therapy was started 1 day after LASIK in one patient,5 but the recurrence occurred the day after. Final visual acuity was 6/6 in one case,5 and two cases needed penetrating keratoplasty because of perforated ulcer6 and one case with bacterial keratitis.7 Case 1 presented 6 weeks after the LASIK procedure, but case 2 is atypical because of the large interval of 2 years between the LASIK procedure and the reactivation of the ocular HSV disease. Oral acyclovir therapy has been shown to reduce recurrences of HSV stromal keratitis,9 but the benefit of acyclovir extends to patients whose last episode occurred up to 1 year before. None of the three previous reported patients or our two patients had ocular or labialis HSV disease 1 year prior to the LASIK procedure. Reactivation of ocular HSV disease may be an underreported entity, and the supplementation of steroid drops that LASIK patients sometimes receive can mask the florid typical picture of stromal disease and be enough for resolution of the attack. Furthermore, prolonged steroid regimen after LASIK can potentiate viral replication if viral shedding occurs. Patients with a history of ocular or nonocular HSV disease undergoing refractive procedures need to be informed of the remote risk of disease reactivation. A prophylaxis of systemic antiviral therapy before and after the procedure may be necessary, but the time of onset and discontinuation of the treatment are unknown to date. Perhaps patients with even a remote history of HSV should not be on a prolonged steroid regimen. Appropriate management of this complication is crucial for maintaining good postoperative visual results.

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references

1. Herpetic eye Disease Study Group. Psy-chological stress and other potential trig-gers for recurrences of herpes simplex virus eye infections. Arch Ophthalmol. 2000;118:1617-1625.

2. Pepose JS, Laycock KA, Miller JK, Chansue e, Lenze eJ, Gans LA, Smith Me. Reactiva-tion of latent herpes simplex virus by ex-cimer laser photokeratectomy. Am J Oph-thalmol. 1992;114:45-50.

3. Dhaliwal DK, Barnhorst DA Jr, Romanowski eG, Rehkopf PG, Gordon YJ. efficient reac-tivation of latent herpes simplex virus type 1 infection by excimer laser keratectomy in the experimental rabbit ocular model. Am J Ophthalmol. 1998;125:488-492.

4. Dhaliwal DK, Romanowski eG, Yates KA, Hu D, Goldstein M, Gordon YJ. experi-mental laser-assisted in situ keratomi-leusis induces the reactivation of latent herpes simplex virus. Am J Ophthalmol. 2001;131:506-507.

5. Davidorf JM. Herpes simplex keratitis after LASIK. J Refract Surg. 1998;14:667.

6. Gupta V, Dada T, Vajpayee RB, Sharma N, Dada VK. Polymicrobial keratitis after la-ser in situ keratomileusis. J Refract Surg. 2001;17:147-148.

7. Perry HD, Doshi SJ, Donnenfeld eD, Levin-son DH, Cameron CD. Herpes simplex re-activation following laser in situ keratomi-leusis and subsequent corneal perforation. CLAO J. 2002;28:69-71.

8. Dhaliwal DK, Romanowski eG, Yates KA, Hu D, Mah FS, Fish DN, Gordon YJ. Valacyclo-vir inhibition of recovery of ocular herpes simplex virus type 1 after experimental re-activation by laser in situ keratomileusis. J Cataract Refract Surg. 2001;27:1288-1293.

9. Herpetic eye Disease Study Group. Oral acyclovir for herpes simplex virus eye dis-ease: effect on prevention of epithelial keratitis and stromal keratitis. Arch Oph-thalmol. 2000;118:1030-1036.

GeNeRAL DISCUSSION

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Refractive surgery is a procedure for patients who are motivated not to use optical correction in the form of glasses or contact lenses.1-3 Satisfaction from the procedures is multi-factorial and sometimes difficult to gauge.1, 3-6 It is imperative to collect and analyze outcomes of different treatment modalities. The purpose of this thesis is manifold: 1. As a control of “how well we perform as surgeons”, do we deliver the results we think we do? 2. As an analysis of how new technologies or variations on other technologies are performing. 3. evaluation of the severity of the side-effects of the technologies we use. 4. Assessing whether our technologies are acceptable in terms of benefit-risk ratio?

In terms of relatively simple parameters like Uncorrected Distance Visual Acuity (UDVA) we are achieving better than before.7-9 In the evaluation of the Advanced Personalized Nomogram we have shown that we can improve the uncorrected visual acuity post-operatively versus the best corrected visual acuity pre-operatively in 22% of patients.10 We have shown that overcorrection with this form of wavefront guided ablations is reduced to 2.8%.10 This is an improvement for those patients. The advantages are clear; more accurate post-operative outcomes, less over corrections, which means less enhancement procedures. The results are in agreement with other literature on the same nomogram11, and we have independently shown that the newer laser nomogram assists in achieving better outcomes.12 Possibly, the improvement compensates for loss of vision that may have occurred as a result of the laser procedure in some of the other 78%, that is, those who did not gain lines of vision, but did not lose lines. This is in line with the “under-promise – over-deliver” adage. One possible weakness of this study is the fact that we studied our results consecutively in the first 100 eyes. One might say that this is a small sample size. Common practice in refractive surgery is to continuously adjust laser nomograms to surgeon factors. Adjustments to nomograms are normally made after 20 to 30 eyes treated. In this aspect, we supplied data on a large enough sample. Is there another explanation for the improved visual acuity, besides the technology used? Detractors can say that the pre-operative visual acuity was biased to be less, while the post-operative visual acuity is biased to a better acuity. Contact lens wear could play a minor role, as our patients are required to come in after they have been ‘weaned’ of their contact lenses. In terms of visual acuity, this might have contributed to a slightly lower Corrected Distance Visual Acuity (CDVA). Testing was done independently by technicians, who are not involved with the analysis. Data analysis in refractive surgery is done continuously, and prospectively. There are official guidelines for the data set that needs to be recorded. As such we have complied with the rules of the profession. The fact that the data was analyzed retrospectively is thus not problematic, because the data we analyzed are the data that are in the standard of data collection. Missing data are a problem in the long term: satisfied patients return less often for follow up visits. This is well know, but not well described in the literature. The other issue is; are the improved outcomes for the myopic laser treatments only caused by the fact that a wavefront guided nomogram was used? I don’t think so. Together with each new nomogram, other software and hardware improvements are installed in the laser. Iris recognition has improved, and the

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eyetracker technology is also advancing. Consistent with the literature, we improved our results, based on the combination of improved ablation nomograms, together with improved tracking and eye recognition technology.13 In the case of bioptics treatments, two factors are very important. One factor is the fact that the refractive error is usually small, and UCDA is usually acceptable in terms of legal vision for driving, but not as good as the patient wants it to be. The other factor is the fact that the refractive error is difficult to measure with our newer technology like the wavefront aberrometry. Setting indications for a refractive error that improves CDVA helps in deciding “how low do we go” in terms of the refractive error. The use of standard laser treatments, and ignoring wavefront aberrations on purpose, has permitted a mode of operation in which we usually achieve the target refraction and visual acuity that goes with it. In the article one can see that nearly 10% of patients do not achieve target refraction. This means that the most common side effect, that is, a residual refraction, occurs in nearly 10%. These errors are usually solved with a surgical enhancement procedure. The downside is a relative high incidence of a side effect, and the risk of incurring more complications, because another surgical procedure needs to be done in order to achieve the refractive goal. This is the most serious problem with bioptics. In due time, indications for doing bioptics will be better defined in the literature. Together with this, we do already see that newer intraocular lenses are being manufactured and used, that can pre-operatively address cylindrical refractive errors. The use of multifocal cylindrical lenses, will obviate the need for planned bioptics, and decrease the need for these procedures, by nearly 42.7% (in our hands). So, as we analyze our current practice and results, we see that technology advances outpace our current practice, by implementation of newer and usually better technology.

In terms of quality of vision there is still a lot of work to be done. We have found that straylight is not affected very much by LASIK and LASeK in myopes and hyperopes, when looking at the total group of patients.10, 14-15 Interestingly we do find that some of our patients have an increase in straylight in one or both eyes. In some patients the slit lamp examination shows us clinical findings like flap striae, debris, or haze that explains to us why the straylight is increased. In others we still don’t have an explanation for the findings.10, 14-16 In our myopic patient population we found a baseline increase of the straylight values10, which is consistent with the literature17. Because of our policy to measure straylight only after patients have not been wearing their contact lenses, and warpage of the corneal surface has been sufficiently addressed, we do not think that contact lens wear and weaning contribute to the overall small but significant decrease in straylight. We did find a trend that ablation thickness is possibly related to the decrease in straylight. Our sample size was not large enough to prove this. The hyperopic patient population actually showed data that is consistent with the above analysis: in the hyperopes there is no increase in straylight, but we did not find a decrease. The ablation profile is such, that the central corneal thickness is not affected. This is in accordance with the trend that a decrease in central corneal thickness is possibly a factor in the post-operative decrease in straylight that we found in the myopic population.

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Refractive surgeons, and their patients, are fast adaptors to new technology. Such is also the case with concepts like straylight. Research of straylight evolved in the 1960-ies. After decades of research straylight is slowly becoming clinically relevant in ophthalmology. Technology is being invented that reliably and repeatedly measures straylight with an instrument clinicians can easily use.18-28 Although the technology has not been completely proven, with which I agree, I find, that understanding of the concept, and availability of the test helps to some degree to understand what is bothering the patient. Sometimes it may even help in the decision-process of whether or not to perform surgery. It is clear, that a lot of work still needs to be done, before straylight measurements will become an accepted part of the ophthalmic examination routine.

Complications remain part of surgery.3, 29-32 The best way to deal with a complication is by prevention. This is largely done at the intake of the patient, by measuring and testing, and also by means of communicating with the patient – does the level of expectations correlate with our level of performance? Complications need to be charted30 and their treatment needs to be shared with peers.33-35 This in order to help the individual patients, but also to prevent future recurrence, and set guidelines on how to treat complications.33-36 In our case series on epithelial ingrowth removal, we have shown that the decrease in straylight is actually much larger than the improvement in Snellen visual acuity. Straylight will not soon become a sole reason for removal of ingrowth, as the indications for removal have been defined.35 Pre-operative risk assessment is probably the most important tool in reducing complications. The risk of reactivation of herpes keratitis after LASIK illustrates how sometimes, this cannot be done pre-operatively, and needs to be addressed when it occurs.37

Is the risk of side-effect or complications worth the benefit of unaided vision? This question is answered by the millions of people who chose to have a procedure done. This is a very philosophical question, and I am unsure of the answer. I am aware however of the drive people have to undergo these procedures. It is imperative as a professional group to ensure safe implementation of the technologies. In the Netherlands, the Dutch Society of Refractive Surgeons has admirably developed clear guidelines and registration of refractive surgeons.38 This has developed out of the tension between a conservative environment in which ophthalmologists are educated and working, and the demand of the public to embrace new technologies. This tension is not going to be resolved, as long as technologies are being developed and implemented. This tension did bring about an environment in the Netherlands, in which the professional organization tries to ensure patient safety by actively producing, controlling adherence to, and updating those guidelines.

The wider view is to look where the development and implementation of the new technologies lead us to. In my understanding, all the improvements in technology and surgical results in refractive surgery slowly become accepted by cataract surgeons and our patients. We see increasing demand from our patients, to use newer technology, and to provide better vision after cataract surgery. Refractive surgery and cataract surgery are slowly converging to a single goal, of emmetropia without presbyopia,

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with good visual quality in terms of straylight and patient satisfaction. The speed of this converging movement depends on environmental factors, such as insurance and government guided restrictions, speed of development of newer technologies, and maturation of the clinical practice of measuring visual acuity and visual quality, and the subjective assessment thereof.

references1. McGhee CN, Craig JP, Sachdev N, Weed

KH, Brown AD. Functional, psychologi-cal, and satisfaction outcomes of laser in situ keratomileusis for high myopia. Journal of cataract and refractive surgery 2000;26:497-509.

2. Schallhorn SC, Farjo AA, Huang D, et al. Wavefront-guided LASIK for the correction of primary myopia and astigmatism a report by the American Academy of Ophthalmol-ogy. Ophthalmology 2008;115:1249-61.

3. Solomon KD, Fernandez de Castro Le, Sandoval HP, et al. LASIK world literature review: quality of life and patient satisfac-tion. Ophthalmology 2009;116:691-701.

4. Bailey MD, Mitchell GL, Dhaliwal DK, et al. Reasons patients recommend laser in situ keratomileusis. Journal of cataract and re-fractive surgery 2004;30:1861-6.

5. Pesudovs K, Gothwal VK, Wright T, Lam-oureux eL. Remediating serious flaws in the National eye Institute Visual Function Questionnaire. Journal of cataract and re-fractive surgery 2010;36:718-32.

6. Rubin GS, Bandeen-Roche K, Huang GH, et al. The association of multiple visual im-pairments with self-reported visual disabil-ity: See project. Invest Ophthalmol Vis Sci 2001;42:64-72.

7. Awwad ST, el-Kateb M, Bowman RW, Cav-anagh HD, McCulley JP. Wavefront-guided laser in situ keratomileusis with the Alcon CustomCornea and the VISX Custom-Vue: three-month results. J Refract Surg 2004;20:S606-13.

8. Durrie DS, Stahl J. Randomized comparison of custom laser in situ keratomileusis with the Alcon CustomCornea and the Bausch & Lomb Zyoptix systems: one-month re-sults. J Refract Surg 2004;20:S614-8.

9. Venter J. Wavefront-guided LASIK with the NIDeK NAVeX platform for the cor-rection of myopia and myopic astigmatism with 6-month follow-up. J Refract Surg 2005;21:S640-5.

10. Lapid-Gortzak R, van der Linden JW, van der Meulen I, Nieuwendaal C, van den Berg T. Straylight measurements in laser in situ keratomileusis and laser-assisted subepithelial keratectomy for myopia. Journal of cataract and refractive surgery 2010;36:465-71.

11. Subbaram MV, MacRae SM. Customized LASIK treatment for myopia based on pr-eoperative manifest refraction and higher order aberrometry: the Rochester nomo-gram. J Refract Surg 2007;23:435-41.

12. Lapid-Gortzak R, van der Linden JW, van der Meulen IJ, Nieuwendaal CP. Advanced personalized nomogram for myopic laser surgery: first 100 eyes. Journal of cataract and refractive surgery 2008;34:1881-5.

13. Netto MV, Dupps W, Jr., Wilson Se. Wave-front-guided ablation: evidence for effica-cy compared to traditional ablation. Am J Ophthalmol 2006;141:360-8.

14. Lorente-Velazquez A, Nieto-Bona A, Col-lar CV, Gutierrez Ortega AR. Intraocular straylight and contrast sensitivity (1/2) and 6 months after laser in situ keratomileusis. eye Contact Lens 2010;36:152-5.

15. Lapid-Gortzak R, van der Linden, J.W., van der Meulen, I.J.e., Nieuwendaal, C.P., Mourits, M.P., van den Berg, T.J.T.P. Stray-light before and after hyperopic LASIK and LASeK. Journal of cataract and refractive surgery in Press

16. Beerthuizen JJ, Franssen L, Landesz M, van den Berg TJ. Straylight values 1 month after laser in situ keratomileusis and photorefrac-tive keratectomy. Journal of cataract and re-fractive surgery 2007;33:779-83.

17. van der Meulen IJ, engelbrecht LA, van Vliet JM, et al. Straylight measure-ments in contact lens wear. Cornea 2010;29:516-22.

18. Coppens Je, Franssen L, van den Berg TJ. Wavelength dependence of intraoc-ular straylight. exp eye Res 2006;82: 688-92.

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19. Coppens Je, Franssen L, van Rijn LJ, van den Berg TJ. Reliability of the compensa-tion comparison stray-light measurement method. J Biomed Opt 2006;11:34027.

20. Franssen L, Coppens Je, van den Berg TJ. Compensation comparison method for as-sessment of retinal straylight. Invest Oph-thalmol Vis Sci 2006;47:768-76.

21. Franssen L, Tabernero J, Coppens Je, van den Berg TJ. Pupil size and retinal stray-light in the normal eye. Invest Ophthalmol Vis Sci 2007;48:2375-82.

22. van den Berg TJ. Importance of pathologi-cal intraocular light scatter for visual dis-ability. Doc Ophthalmol 1986;61:327-33.

23. van den Berg TJ. On the relation between glare and straylight. Doc Ophthalmol 1991;78:177-81.

24. Van den Berg TJ. On the relation between intraocular straylight and visual function parameters. Invest Ophthalmol Vis Sci 1994;35:2659-61.

25. van den Berg TJ. Analysis of intraocular straylight, especially in relation to age. Op-tom Vis Sci 1995;72:52-9.

26. van den Berg TJ, Franssen L, Coppens Je. Straylight in the human eye: testing objec-tivity and optical character of the psycho-physical measurement. Ophthalmic Physi-ol Opt 2009;29:345-50.

27. van den Berg TJ, JK IJ, de Waard PW. De-pendence of intraocular straylight on pig-mentation and light transmission through the ocular wall. Vision Res 1991;31:1361-7.

28. Van Den Berg TJ, Van Rijn LJ, Michael R, et al. Straylight effects with aging and lens extrac-tion. Am J Ophthalmol 2007;144:358-63.

29. Gimbel HV, Penno ee, van Westenbrugge JA, Ferensowicz M, Furlong MT. Incidence and management of intraoperative and early postoperative complications in 1000 consecutive laser in situ keratomileusis cases. Ophthalmology 1998;105:1839-47; discussion 47-8.

30. Levinson BA, Rapuano CJ, Cohen eJ, Hammersmith KM, Ayres BD, Laibson PR. Referrals to the Wills eye Institute Cor-nea Service after laser in situ keratomi-leusis: reasons for patient dissatisfaction. Journal of cataract and refractive surgery 2008;34:32-9.

31. Rosen eS. Risk management in refractive lens exchange. Journal of cataract and re-fractive surgery 2008;34:1613-4.

32. Stulting RD, Carr JD, Thompson KP, War-ing GO, 3rd, Wiley WM, Walker JG. Com-plications of laser in situ keratomileusis for the correction of myopia. Ophthalmology 1999;106:13-20.

33. Kuo IC, Jabbur NS, O’Brien TP. Photore-fractive keratectomy for refractory laser in situ keratomileusis flap striae. Jour-nal of cataract and refractive surgery 2008;34:330-3.

34. Jabbur NS, Myrowitz e, Wexler JL, O’Brien TP. Outcome of second surgery in LASIK cases aborted due to flap complications. Journal of cataract and refractive surgery 2004;30:993-9.

35. Jabbur NS, Chicani CF, Kuo IC, O’Brien TP. Risk factors in interface epithelialization after laser in situ keratomileusis. J Refract Surg 2004;20:343-8.

36. Solomon R, Donnenfeld eD, Azar DT, et al. Infectious keratitis after laser in situ keratomileusis: results of an ASCRS survey. Journal of cataract and refractive surgery 2003;29:2001-6.

37. Levy J, Lapid-Gortzak R, Klemperer I, Lif-shitz T. Herpes simplex virus keratitis after laser in situ keratomileusis. J Refract Surg 2005;21:400-2.

38. NGRC. http://www.oogheelkunde.org/professionals/evidence-based-richtlijnen/item?url Proxy=/patienten/patientenvoor-lichting/richtlijnen2/consensus-refractie-chirurgie-2009&objectSynopsis=#96oYeANee6OoaSeMfu79Sg. 2009.

SUMMARY

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Patients who seek a refractive procedure are motivated to undergo an elective procedure that will enhance their vision without the need for optical correction. In the majority of cases the outcomes are acceptable to excellent, with high satisfaction in terms of improved uncorrected vision, recreation, and comfort. Side effects are well known.

Does patient satisfaction correlate with visual quality? This depends on the definition used. Visual quality and patient satisfaction depend on patient expectations, and patient experience with vision. Visual quality is determined by physical and psychological phenomena.

In the introduction, in chapter 1, the history and development of refractive surgery and some of the technologies used are described. Visual quality parameters are described together with explanations of the technologies that allow for measurement of these parameters. The relevant questions posed are whether the newer laser technologies improve visual acuity and visual quality. The effect corneal laser surgery has on straylight is introduced. Complications and safety of refractive surgery are described.

Newer wavefront guided laser nomograms, have shown a consistent improvement of outcomes in terms of target refraction and Snellen acuity. Literature on this is scant and possibly biased as it is often produced by people who are related to the companies that develop these nomograms.

chapter 2 shows our data in the independent clinical setting, of how well this nomogram performs. In evaluating the Advanced Personalized Nomogram, we have shown that in nearly 1-in-5 patients we are able to achieve an improved uncorrected post-operative visual acuity, as compared to pre-operative best corrected visual acuity. Our findings affirm that newer laser nomograms perform better. In wavefront guided ablations, the eyes’ aberrations are treated for, but a corrective factor for the aberrations induced by the laser treatment is also accounted for. We see that enhancement rates from previous wavefront guided treatments decrease from nearly 1-in-4 eyes, to 1-in-35.7 eyes. This decrease in the rate of enhancements means a significant reduction in the most common side effect of laser refractive surgery. Wavefront guided treatments reduce overcorrections, which are the foremost cause of retreatment and patient dissatisfaction. Retreatment is the second most common complication or side effect of refractive surgery. Reducing retreatment rates is very important in increasing safety and predictability of refractive surgery.

In chapter 3 evaluation of bioptics procedures after multifocal diffractive apodized lens implantation is shown, does it make sense to treat a mean residual refraction that is less than 1 D in spherical equivalent refraction? Our results show that it is safe and efficacious to do so, and that patient satisfaction increases. Both LASIK and LASeK can be done. The discussion that has not yet been resolved is which laser nomogram to use. In our opinion, one should treat the manifest spherocylindrical refraction. Wavefront measurements in multifocal pseudophakic eyes cannot be reliably and repeatedly done. Also most wavefront aberrometers will either measure, or extrapolate the

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aberration beyond 6 mm, which is the optic diameter of the intraocular lens used. As a result one would likely correct for non-existing aberrations centrally on the cornea, and thus reduce the visual acuity or increase the manifest refractive error, or both. Another reason is that most lenses we implant have a negative spherical aberration purposely made to induce a little bit more of depth of focus. If one tries to correct this with a wavefront guided treatment, we might actually lose that benefit.

Straylight, which is by definition disability glare is an objective measure for quality of vision. It was tested in a population of myopic and hyperopic patients before and after either LASIK or LASeK.

In chapter 4 we describe the behavior of straylight in myopic laser ablations, both in LASIK and in LASeK. We found a small, but statistically significant decrease in straylight in these patients. The clinical significance is that straylight overall does not increase, which was contrary to expectations. In some eyes we could find an increase in straylight and could sometimes relate it to specific findings in the cornea. In some eyes we could not relate an increase in straylight to clinical findings. This can be explained by the fact that the slit lamp examination, which is the golden standard for ocular examination, relies on backscatter for visualization, while straylight is a function of forward scatter of light in the eye. We think that the decrease in straylight is mostly related to a central decrease in corneal thickness, following ablation. The relation between ablation depth and the reduction in straylight was a trend, but was not statistically significant.

In hyperopic ablations, as described in chapter 5, we found no change in straylight in eyes that had LASIK or LASeK. This is consistent with our findings in the myopic treatments. Again in some eyes straylight was increased, and this could, some of the time, be related to clinical findings at the slit lamp examination. In hyperopic ablations, the center of the cornea does not change very much in thickness, so these findings are again consistent with the findings that straylight decreased on average in the myopic eyes.

This is very good news for our patients, as disability glare is one of the quality of vision parameters that is potentially endangered by doing surgery. It will take more research and time before the ophthalmological community will adapt to and accept straylight as a complementary test to visual acuity testing. early adaptors, like me, have already implemented its use in daily practice. I feel this is an instrument than enhances decision making under certain circumstances.

We also looked at straylight under circumstances of a potentially serious complication, such as epithelial ingrowth. We could relate the clinical findings and improvement to straylight findings. This is just part of the research work that will need to be done – to show the clinical uses for straylight testing.

In chapter 6 we describe the treatment of epithelial ingrowth, with the ensuing improvement in visual acuity, and refractive error, but also a major improvement in straylight. The incidence and indications to treat, and techniques to treat epithelial ingrowth is reviewed.

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chapter 7 elaborates on reactivation of herpes keratitis after LASIK. Herpes reactivation is a rare post-operative complication, but needs to be diagnosed and treated in due time.

Refractive surgery is a rapidly changing and evolving subspecialty within ophthalmology. It deals with innovative technique and cutting edge surgeries. In its nature it appeals to patients who adapt rapidly and easily to new technologies and who are motivated by their wish not to wear optic aids. The practice of refractive surgery strives for exemplary accuracy in outcomes, and major efforts in reducing potential complications. The results of refractive surgery are daily being translated into improvements in cataract surgery. Patients are aware of the possibilities and have become more demanding. We experience a trend in which refractive surgery and cataract surgery as we know it converge. This exchange will undoubtedly strengthen both fields.

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Patiënten die een refractiechirurgische ingreep zoeken, zijn gemotiveerd om een ingreep te ondergaan, om hun ongecorrigeerde gezichtsvermogen te verbeteren. In de meerderheid van de gevallen zijn de resultaten van deze ingrepen acceptabel tot uitstekend, met hoge tevredenheid in termen van ongecorrigeerde gezichtsscherpte, recreatie en comfort. De neveneffecten zijn bekend.

Is er een correlatie tussen patiënttevredenheid en kwaliteit van zien? Dit hangt af van de definitie. Kwaliteit van zien en patiëntentevredenheid zijn gebaseerd op de verwachtingen van de patiënten en de ervaring met wat ze zien. Kwaliteit van zien wordt bepaald door zowel fysische als door psychologische fenomenen.

In de introductie, in hoofdstuk 1, worden de geschiedenis en ontwikkeling van de refractiechirurgie samengevat. De verschillende technologieën die nodig zijn voor de toepassing van de refractiechirurgie worden uitgelegd. Visuele kwaliteitsparameters worden technisch beschreven en toegelicht met hun klinische toepassingen. De relevante vragen zijn of de vernieuwingen en verbeteringen in lasers zich vertalen naar een scherper gezichtsvermogen en betere kwaliteit van zien. Ook worden de relatie tussen strooilicht, die verblinding meet en kwantificeert en laser- refractiechirurgie besproken. Neveneffecten en complicaties van refractiechirurgie worden eveneens besproken.

De nieuwe ‘wavefront guided’ lasernomogrammen laten consistent een verbetering zien in het behalen van de doelrefractie en gezichtsscherpte op de Snellen kaart. De literatuur die deze verbeteringen beschrijft is niet heel uitgebreid en komt van de hand van de mensen die de nomogrammen maken. De resultaten van de behandeling van 100 ogen met het “Advanced Personalized Nomogram”, een wavefront gebaseerd nomogram, in hoofdstuk 2, laat zien, dat de resultaten inderdaad erg nauwkeurig zijn. In 2.8 % wordt nog een overcorrectie van meer dan 1 Dioptrie gevonden, terwijl dat voorheen in het nomogram daarvoor nog bijna 22% was. Dit betekent, dat nabehandelingen, die het meest voorkomende neveneffect zijn van een behandeling, significant zijn teruggedrongen zijn. Ook zien we dat in bijna 1 op de 5 ogen een betere gezichtsscherpte wordt bereikt. Deze resultaten zijn in overeenstemming met de bevindingen in de literatuur en de constatering dat met nieuwere laser nomogrammen betere resultaten worden geboekt.

In het derde hoofdstuk staat de bioptics behandeling centraal, namelijk de behandeling, zoals beschreven in het artikel, is een LASeK- of LASIK- behandeling na een multifocale lens implantatie. De voornaamste reden voor ontevredenheid na refractieve lens ingrepen, is een resterende kleine refractie afwijking, die de optimale visus vermindert. Het blijkt, dat bijna 10% van de patiënten een nabehandeling nodig heeft. De vraag is, hoe groot of hoe klein moet deze afwijking zijn om toch nog te behandelen met een laser, aangezien de limiet van de nauwkeurigheid van de laser hiermee getest wordt. Het blijkt, dat de behandeling voorspelbaar is, en goede resultaten geeft. De tevredenheid van de patiënten is groot: zij bereiken immers het doel dat zij wilden bereiken – een goede visus zonder bril voor ver en nabij.

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Hoofstuk 4 en 5 gaan over het meten van strooilicht bij LASIK- en LASeK- behandelingen. In hoofdstuk 4 bij myope behandelingen en in hoofdstuk 5 bij hypermetrope behandelingen. Strooilicht is een parameter voor de kwaliteit van het zien en meet verblinding. De verwachting was, dat strooilicht verhoogd zou zijn na de ingreep. De basis voor deze verwachting is het feit, dat het weefsel door de ingreep van structuur verandert. Bij behandelingen van bijzienden zien we, tot onze verrassing, dat er een kleine, maar statistisch significante verlaging is van het strooilicht na de ingreep. De enige verklaring hiervoor, die wij konden vinden, was het feit dat het hoornvlies centraal dunner was geworden. Deze trend was statistisch niet significant. er waren echter ook een aantal ogen, waarbij het wel strooilicht verhoogd was. Meestal konden daarvoor in deze ogen verklaringen worden gevonden zoals striae of haze, die het verhoogde strooilicht konden verklaren. Niet in alle ogen met verhoogd strooilicht, kon deze bevinding verklaard worden door klinisch onderzoek met de spleetlamp. De reden hiervoor is het verschil tussen voorwaartse lichtverstrooiing, die gemeten wordt bij strooilicht en de terugkaatsende aard van het licht, dat we zien met de spleetlamp. Men kan stellen, dat strooilicht niet verhoogd is na LASIK en LASeK, tenzij er een specifiek probleem is.

Het onderzoek naar strooilicht bij de hyperope LASIK- en LASeK- behandeling laat een beeld zien, dat overeenkomt met de resultaten van de myope groep. Strooilicht is niet verhoogd in deze groep. Weer was de verwachting dat strooilicht verhoogd zou zijn, vanwege structurele veranderingen in het weefsel. Ook hier werd dit effect niet gevonden. De laserablatie bij hyperope ogen is meer perifeer, waardoor er centraal op het hoornvlies bijna geen weefsel wordt verwijderd. Dit verklaart waarom er geen verlaging werd gezien van het strooilicht. Bij andere onderzoeken is gebleken dat het dragen van contactlenzen strooilicht verhoogt. Hierdoor zou men kunnen denken, dat omdat de meeste mensen vóór een laser behandeling contactlensdragers zijn het preoperatieve strooilicht eigenlijk verhoogd is en zo een postoperatieve verhoging maskeert. De manier van meten bij de patiënten, die gedaan werd na de tijd was waarin contactlenzen nog een effect kunnen hebben, sluit dit effect uit.

In hoofdstuk 6 wordt het effect van een complicatie en het oplossen ervan beschreven in termen van gezichtsscherpte en strooilicht. epitheel ingroei is een zeldzame, maar potentieel ernstige complicatie. Door het weghalen van het ingegroeide weefsel en het mogelijk maken van een normale aanhechting van de corneaflap, wordt niet alleen structureel een verbetering aangebracht in het hoornvlies, maar wordt de gezichtsscherpte verbeterd. Frappant is hierbij, dat de verbetering van het strooilicht (dus de verlaging ervan) relatief een veel groter effect is, dan het effect op de gezichtsscherpte. Dit laat weer zien dat strooilicht een parameter is van de kwaliteit van het zien.

In hoofdstuk 7 wordt een zeer zeldzame complicatie na LASIK beschreven: een reactivatie van een dormante herpes keratitis. De meeste volwassen mensen hebben ooit een herpes infectie gehad. Bij sommigen geïnfecteerden treedt later een reactivatie op in de vorm van een koortslip of een herpetische keratitis. Als dit gebeurt

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na een LASIK-behandeling, is het effect op het gezichtsvermogen zeer ernstig door vervorming van de LASIK flap en litteken vorming. Dit is bij uitstek een complicatie die vermeden moet worden door een goede preoperatieve anamnese en onderzoek. Zelfs dan is het moeilijk om uit te sluiten of een patiënt extra risico loopt.

Refractiechirurgie is een gebied van de oogheelkunde dat snel verandert en zich ontwikkelt. Het is een gebied waarin nieuwe technieken snel ingevoerd worden. Door de wens van de patiënten om zonder optische hulpmiddelen te kunnen leven, hebben nieuwe technieken in de refractiechirurgie een bijzondere aantrekkingskracht op mensen die zich snel kunnen aanpassen aan vernieuwingen. De dagelijkse praktijk van de refractiechirurgie bestaat uit het bereiken van zeer nauwkeurige resultaten gekoppeld aan een grote inspanning om complicaties te voorkomen. Deze resultaten van de refractiechirurgie beïnvloeden de cataractchirurgie: patiënten weten vaker en beter wat de mogelijkheden zijn en eisen deze dan ook voor zichzelf. Wij ervaren een trend waarin refractiechirurgie en cataractchirurgie elkaar vaak overlappen en aanvullen. Dit zal de patiënten uiteindelijk ten goede komen.

Documents

UvA-DARE (Digital Academic Repository) Visual quality … · to attain this, such as intra-corneal inlays, or intrastromal femtosecond treatments like 10 GeNeRAL INTRODUCTION. Intracor,