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The Eye Digest (www.agingeye.net). No part of this article may be copied without permission.

The Eye Digest is published by University of Illinois Eye & Ear Infirmary Physicians. Full text

of this article is available at The Eye Digest LASIK Page.

Laser Vision Correction LASIK, Epi-LASIK and LASEK

The goal of 'The Eye Digest' is to provide objective information to the public about LASIK

surgery. Given the extensive publication record and surgical experience, we believe we are

qualified to provide you with credible and unbiased information on all aspects of laser visioncorrection.

LASIK, Epi-LASIK & LASEK books written by Dr. Dimitri Azar - Editor of 'The Eye Digest'.

Overview of Laser Vision Correction Surgery - Essential FactsSeveral effective options for laser refractive surgery are available. Navigating the complex arrayof options can be difficult, but more choices also bring the opportunity to meet more of the needs

of an individual patient. The choices can broadly be divided into:

Lamellar (Laser-Assisted In Situ Keratomileusis - LASIK)LASIK is lamellar laser refractive surgery in which the excimer laser ablation is done under a

partial-thickness lamellar corneal flap. Until recently, the lamellar flap could only be made with amicrokeratome. The femtosecond laser provides more accuracy in flap thickness than previous

methods and it might be more reliable in cases of steep or flat corneas.

Surface (photorefractive keratectomy [PRK], laser epithelial keratomileusis [LASEK],

and Epi-LASIK) ablation.

In these procedure the excimer laser is used to ablate the most anterior portion of the corneal

stroma. These procedures do not require a partial thickness cut into the stroma. Surface ablationmethods differ in the way the epithelial layer is handled. In PRK the epithelium is removed, a

large epithelial defect ensues, and healing occurs by migration of surrounding epithelium

(usually within a week). In LASEK and Epi-LASIK surgery, the patient's epithelium is not

removed. The epithelium is lifted as a sheet and then after laser ablation, the epithelial sheet isre-placed to cover the treated area. In LASEK dilute alcohol is used to loosen the epithelium.

LASEK procedure was developed by Dr. Dimitri Azar, Editor ofThe Eye Digest. In Epi-LASIK,

a purely mechanical means of epithelial dissection (using Epikeratome) allows the creation of theepithelial sheet.

Compared with surface ablation, LASIK results in earlier and faster improvement of uncorrected

visual acuity, and has less (or almost no) postoperative discomfort, improved stability, and

predictability. With LASIK, however, the risks of flap-related complications (wrinkles, debris, folds, buttonhole, and diffuse lamellar keratitis) may be associated with the creation of the

lamellar flap.

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Conventional versus wavefront-guided treatment: Regardless of whether the surgeon does

LASIK or surface ablation, there is an additional choice in how the laser will be applied to the

cornea. Conventional ablations make use of data obtained during manifest and cycloplegicrefractions. This data, that is generated by humans (surgeon, technician etc) based on their

examination of your eye, is what tells the laser how much to treat and how to treat. The ablation

profile will contain a spherical component and an astigmatic component. Conventional ablationsessentially treat what glasses have been treating for hundreds of years. Wavefront-guided

treatments allow optical properties beyond spherical and cylindrical defocus to be corrected.

Wavefront aberrometers (automated machines) capture data that describe the optical aberrationsof a patient's eye. This data, that is generated by an automated machine (wavefront aberrometer)

based on an average of 3 automated recordings, is what tells the laser how much to treat and how

to treat.

Whether the additional information obtained with wavefront-guided treatments is translated into

better ablations and improved acuity compared with conventional LASIK can be determined by

comparing the FDA trials data. In wavefront-guided LASIK, 89% of patients achieved

uncorrected visual acuities of 20/20 or better . By contrast, with conventional treatment, patientsreached 20/20 or better only 72% of the time. Therefore more people can expect to achieve

uncorrected vision of 20/20 with wavefront-guided LASIK. The likely reason for this differenceis that wavefront-guided treatments treat higher order aberrations as well (conventional

treatments do not treat higher order aberrations).

Will I have 20/20 vision without glasses after LASIK?

If the myopia is low to moderate (i.e. -7 D or less), then 96% patients achieve uncorrected visual

acuities better than 20/40, however only 72% of patients achieve vision equal to or better than20/20. As mentioned earlier, more people achieve 20/20 vision with wavefront-guided treatment.

If the myopia is high (i.e. more than -7 D ), then 89% patients achieve uncorrected visual acuitiesbetter than 20/40, however only 48% of patients achieve vision equal to or better than 20/20.Note that the uncorrected vision results in high myopes is not as good as in low myopes (FDA

data). LASIK and surface ablation have largely similar vision outcomes. Therefore, most - but

not all - people will have 20/20 vision after LASIK without glasses. Some people will not be ableto "get rid of glasses" to see 20/20. Taken together, this means that LASIK will almost certainly

reduce your dependence on glasses and contact lenses, however, there is no certainty and there

can be no guarantee that you will be able to achieve perfect vision without glasses. You have 90

to 95% chance of passing the vision test to get a drivers license without glasses (i.e 20/40 vision)and therefore 90 to 95% chance that you will be able to legally drive without glasses after

LASIK. Our recommendation, however, is that you drive with the best vision that your eyes are

capable of achieving.Serious complications from refractive surgery are rare, as evidenced by the low rate of lossof best spectacle-corrected visual acuity. However, before undergoing any refractive

procedure, you should carefully weigh the risks and benefits based on your own personal

value system, and try to avoid being influenced by friends that have had the procedure or

doctors encouraging you to do so. Remember that, even though rare, complications do

occur.