Lasik, Epi-lasik & Lasek - Laser Vision Correction

© 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 vision correction.

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

Overview of Laser Vision Correction Surgery - Essential Facts Several effective options for laser refractive surgery are available. Navigating the complex array of 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 a microkeratome. 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 ablation methods 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 is re-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 of The Eye Digest. In Epi-LASIK, a purely mechanical means of epithelial dissection (using Epikeratome) allows the creation of the epithelial 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.

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 cycloplegic refractions. 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 ablations essentially 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 aberrations of 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, patients reached 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 difference is 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 than 20/20. 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 acuities better 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 able to "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 loss of 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.