Wavefront-guided Photorefractive Keratectomy to Correct Ametopia following ReSTOR Implantation

Irene C. Kuo, MDAssociate Professor of Ophthalmology

Wilmer Eye Institute

I have no financial interests; research supported by an unrestricted grant from Research to Prevent Blindness, NY, NY

ASCRS 2009, San Francisco, P-191A

Co-authors

• Elliott Myrowitz, OD

• Oliver Schein, MD, MPH, MBA

• Roy S. Chuck, MD, PhD (consultant for Advanced Medical Optics, Inc., and Alcon Laboratories, Inc.)

Introduction

• expectations of refractive outcomes after cataract surgery are increasing.

• ametropia can still occur with multifocal lens implantation despite advanced surgical techniques and sophisticated methods to predict intraocular lens power.

Kuo , ASCRS 2009

Introduction

• few reports of excimer laser surgery to correct residual refractive error in patients implanted with multifocal lenses– questions about accuracy of wavefront

acquisition in multifocal lenses, both diffractive and refractive types

Kuo , ASCRS 2009

ReSTOR lens: apodized diffractive, refractive IOL

Two primary focal points--distance and near (approx 3.2 D add power in spectacle plane). 12 diffractive discontinuities (steps) in the anterior surface of the cast-molded acrylic optic provide the diffractive add power. The steps cover the central 3.6 mm diameter of the IOL. The optic from 3.6 mm to the 6.0 mm edge is comprised of a refractive surface dedicated to distance vision. ≤2 mm pupil, 41% distance, 41% near, 18% to higher diffractive orders (with permission from Davison JA, Simpson MJ. History and development of the apodized diffractive intraocular lens. J Cataract Refract Surg 2006;32:849-585).

Methods

• IRB-approved protocol for refractive patients

• thorough preoperative evaluation– detailed medical, ocular, social history– uncorrected and best corrected visual acuity– manifest refraction , cycloplegic refraction– corneal topography, pachymetry– slit-lamp examination, pupillary exam, Schirmer

testing, dilated exam

Kuo, ASCRS 2009

Methods

• Orbscan (Bausch and Lomb)• CustomVue Wavescan (Advanced Medical Optics)

– three or more measurements are obtained with undilated pupil; 5 mm pupil or larger needed for wavescan capture

– measurement where wavefront sphere best matches manifest sphere is chosen for treatment

– physician adjustments to sphere are performed where needed to improve match between manifest and wavefront sphere

Kuo, ASCRS 2009

Methods

• VISX STAR S4 (Advanced Medical Optics) was used in all cases– eye tracker and iris registration were engaged in all

eyes– off-label use of VISX laser in setting of

pseudophakia was discussed with each patient

Kuo, ASCRS 2009

Case• 78-year-old man with bilateral cataracts

– Preoperative Ks 40.27 x 42.99 D in OS at 169 degrees by IOL Master

• November 2006: uncomplicated cataract extraction OS, with 19.5 D ReSTOR SN6AD3 (+4 diopter add in IOL plane) and limbal relaxing incisions

• YAG laser capsulotomy in June 2007

• August 2007: UCVA was 20/40 and BCVA was 20/30 with manifest refraction of -1.25 + 2.00 x 175—wavefront PRK

Kuo, ASCRS 2009

Case

• corneal pachymetry was 580 microns. Keratometry was 41.25 x 42.75 D at 175 by Orbscan

• CustomVue Wavescan showed an RMS of 0.43 µm

• patient underwent wavefront-guided PRK in OS with goal of postoperative emmetropia

• wavefront data from a 5.25 mm pupil was used. Physician adjustment of -0.75 diopters was incorporated in treatment

Kuo, ASCRS 2009

Kuo, ASCRS 2009

Kuo, ASCRS 2009

Results

Post-CE-IOL and pre-PRK Post-PRK

UCVA MR, BCVA near 1-2 months 3-6 months 7-10 months 16 months

UCVA MR, BCVA UCVA MR, BCVA, Near

UCVA MR, BCVA, Near

Case 1OS

20/50 plano+1.25x020 20/20

J6 20/25 -0.50+0.75x145, 20/25

20/25 -0.25, 20/25, J3

20/20 Plano, 20/20, J1+

Case 2OS

OD

20/40

20/40

-1.25+2.00x175 20/30

-0.25+1.50x035, 20/30

J4

J5

20/40

20/40

-0.25+0.25x040,20/40

-0.75+0.50x10020/30

20/25

20/30

-0.25, 20/25, J3

-0.25+0.50x110 20/30 J2+

20/25

20/25

Plano, 20/25, J3 20/25 -0.25 J2

0.25+0.50x090

20/25, J2

Visual acuity of eyes with ReSTOR lens before and after PRK. CE-IOL=cataract extraction with ReSTOR implantation, UCVA=uncorrected Snellen visual acuity, BCVA=best-corrected Snellen visual acuity, MR=manifest refraction, J=Jaeger. All manifest refractions are in diopters.

Kuo, ASCRS 2009

Hartmann-Shack Aberrometer

CCD-Camera Lens Array

Outcoming Wave CCD-Image

With permission from AMO, Inc.

Hartmann-Shack Aberrometer Each Spot or lenslet

lets in lightWaveScan® software

calculates the wavefront map and generates a

wavefront treatment for the laser to follow

Each spot is analyzed as to how the light is traveling in that part of the eye

240 points in a 7 mm pupil

With permission from AMO, Inc.

Why wavefront-guided treatment?

• seems appropriate to correct refractive error after implantation of an aspheric multifocal lens

• offers iris registration– compensates for cyclotorsion and pupil centroid

shift, thus correcting astigmatism more precisely than conventional treatment

Kuo, ASCRS 2009

Role of excimer laser after multifocal lens implantation

• unavailability of toric multifocal lenses

• “refractive surprises”

• range of lens powers for the ReSTOR lenses is smaller than range for monofocal lenses

• any residual refractive error after multifocal lens implantation will affect vision (and contrast sensitivity) at all distances

Kuo, ASCRS 2009

Drawbacks of H-S sensor with multifocal IOL

• diffractive discontinuities in lens may result in locally distorted wavefronts– spatial distribution of stray centroids (just inside or

outside pixel subarray of charge-coupled device) may be hard to predict

– scattering incurred by discrete junctions between diffractive zones

– may lead to overestimation of the optical quality of eyes with diffractive multifocal IOLS

Kuo, ASCRS 2009

Drawbacks of H-S sensor with multifocal IOL

• concentric zones in ReSTOR vs. square microlens array may lead to inaccurate reconstruction of wavefront

Kuo, ASCRS 2009

Drawbacks of H-S sensor

• Perhaps the findings from our three cases will not be true with larger refractive errors and/or with lens tilt/decentration – tilt/decentration may be more deleterious in

aspheric than in spheric lenses– size of capsulorhexis and clarity of posterior

capsule may also interfere with good wavefront capture

Kuo, ASCRS 2009

Why H-S data may still be acceptable

• At the wavelength used, the aberrometer may be unaffected by the diffractive effect of the ReSTOR lens– the higher the wavelength used in the wavefront

sensor, the lower the diffractive efficiency, and the higher the add power

Kuo, ASCRS 2009

Why H-S data may still be acceptable

• the H-S aberrometers seem more likely to produce wavefront results corresponding to the wavefront produced by the distance power of a diffractive IOL

• Hence, the relative lack of “doubling” of spots in H-S images in eyes with the ReSTOR

Kuo, ASCRS 2009

Conclusions

• It is possible to obtain good quality wavefront data in patients with ReSTOR lens and to use such data to design wavefront-guided treatment to maximize uncorrected distance and near visual acuities after ReSTOR– reproducible, well-focused, properly aligned image– wavefront and manifest refractions correlate– Ortiz et al confirmed using another H-S system

Kuo, ASCRS 2009

Conclusions

• It is possible to “mix and match” platforms—one company’s IOL and another company’s wavefont-guided laser

Kuo, ASCRS 2009

Conclusions

• in our cases, PRK was chosen over laser in-situ keratomileusis (LASIK) because of low refractive error and possibility that LASIK flap might induce more aberrations

• However, perhaps not all patients with multifocal IOLs will qualify for wavefront-guided excimer laser treatment• type of IOL, amount of refractive error , corneal

topography, pachymetry

Conclusions

• The three eyes in our series had good quality wavescans which were used for wavefront-guided PRK, with subsequent improvement of UCVA and in one case, BCVA

– delay in achieving best UCVA and BCVA– results of (older) patients undergoing conventional

laser surgery to correct post-cataract surgery ametropia vs. patients who have not had CE-IOL

References• Charman WN, Montés-Micó R, Radhakrishnan H. Problems in the

measurement of wavefront aberration for eyes implanted with diffractive bifocal and multifocal intraocular lenses. J Refract Surg. 2008; 24(3):280-286.

• Davison JA, Simpson MJ. History and development of the apodized diffractive intraocular lens. J Cataract Refract Surg 2006;32:849-585.

• Gatinel D. Limited accuracy of Hartmann-Shack wavefront sensing in eyes with diffractive multifocal IOLs [letter]. J Cataract Refract Surg 2008;34:528

• Jendritza BB, Knorz MC, Morton S. Wavefront-guided excimer laser vision correction after multifocal IOL implantation. J Refract Surg 2008;24:274-279.

References• Ortiz D, Alio J, Bernabeu G, Pongo V. Optical performance of monofocal

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• Atchison DA. Design of aspheric intraocular lenses. Ophthalmol Physiol Opt 1991;11:137-146.

• Altmann GE, Nichamin LD, Lane SS, Pepose JS. Optical performance of 3 intraocular lens designs in the presence of decentration. J Cataract Refract Surg 2005;31:575-585.