AUG 2014

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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EW FEATURE 42 by Ellen Stodola EyeWorld Staff Writer Keratorefractive surgery August 2014 AT A GLANCE • The iDesign's robust and higher resolution system may help patients with irregular corneas. • Topographic ablations can help customize treatment based on the corneal topography and not wavefront. • Using ReLEx SMILE could help decrease the impact on corneal strength and reduce dryness. • CATz stands for custom aspheric treatment zone. It customizes treatment for each patient's corneal shape, adjusts for changes in radial ablation efficiency, and makes no distinction between optical zone and the transition zone in its treatment zone. New technologies for better LASIK and PRK outcomes Technologies such as SMILE, topographic ablations, CATz, and iDesign may be useful in improving outcomes T here are a number of new technologies to improve both LASIK and PRK out- comes. John Vukich, MD, Madison Wis.; Guillermo Rocha, MD, associate professor, University of Manitoba, Manitoba; George O. Waring III, MD, professor emeritus of ophthalmolo- gy, Emory University, Atlanta; and D. Rex Hamilton, MD, associate clinical professor of ophthalmolo- gy and director of the UCLA Laser Refractive Center, Jules Stein Eye Institute, University of California, Los Angeles, discussed some of these new technologies, includ- ing ReLEx (refractive lenticule extraction) SMILE (small incision lenticule extraction) with the VisuMax laser (Carl Zeiss Meditec, Jena, Germany), iDesign (Abbott Medical Optics, AMO, Santa Ana, Calif.), the CATz program (Nidek, Fremont, Calif.), and topographic ablations. New technologies There are already very high stan- dards in terms of correcting with excimer laser ablations, Dr. Vukich said. "Now what it's coming down to are the algorithms of how we measure the refraction and how we translate that into an accurate correction for the cornea." Wavefront-guided treatment is a big step from a general algorithm to a more sophisticated way to under- stand the optical error and not just the refractive error. The next step is to incorporate the medium that you're working on, which is the cornea, he said. Dr. Rocha said the main advantages of the new techniques can be categorized as diagnostic (acquisition of information), soft- ware improvements, and laser deliv- ery. "There has always been a race between what the surgeon can see on diagnostic tests versus what can be treated in a reliable fashion," Dr. Rocha said. "The evolution of these technologies allows us to better diagnose not only corneal topogra- phy, but also high order aberrations of the whole eye." Dr. Rocha added that new lasers create a "more re- fined diagnostic process," which can be linked to the laser software for further physician adjustment and planning. SMILE SMILE is a technique where the fem- tosecond laser is used for the entire refractive treatment, so an excimer laser is not needed, according to Dr. Hamilton. Instead of creating a flap, the surgeon would cut a lenticule out of the mid stroma of the cornea. "That lenticule shape is based on the intended refractive change," he said. There is a side cut down to the edge of the lenticule. You free up the lenticule and pull it out of the side incision, which is typically about 3.5 mm to 4 mm, he said. This technique has a number of advantages, notably the financial advantage of not having to purchase 2 lasers. Another advantage in- volves biomechanics. "The anterior peripheral cornea is the portion of the cornea that holds the most strength," he said. Cutting a LASIK flap through this area weakens the cornea. Using SMILE has less of an effect on the strength of the cornea. Another potential advantage involves the impact on dry eye disease. When creating a LASIK flap, the cut may negatively affect the sensory nerves that contribute to the neuro pathway for producing tears. With SMILE, you're avoiding cutting down from the surface and not interrupting that neuro sensory pathway and having less affect on dry eye, Dr. Hamilton said. Currently, this technique is un- dergoing an FDA trial for spherical myopia, and there will be a myopic astigmatism FDA trial in the future. Topographic ablations In terms of topographic ablation, Dr. Hamilton said there are a couple of indications for this technology. The FDA trial sponsored by Alcon (Fort Worth, Texas) in the U.S. has approved the technique for certain indications. One instance where this is use- ful is with an irregular cornea shape where a standard myopic ablation does not achieve the best vision and you need to customize treatment. However, this indication may not apply to a large number of patients. Dr. Hamilton said that a more interesting use would be for the standard patient and doing topog- raphy-guided ablations "for the Monthly Pulse Keeping a Pulse on Ophthalmology T he topic of this Monthly Pulse Survey was LASIK/keratorefractive surgery. We asked, "What IOL calculation technique are you using to determine the IOL power in patients who have undergone previous LASIK?" A large majority of respondents said they use the ASCRS IOL calculation website. When asked, "What surgical technique do you use the most for correcting refractive results in patients with residual refractive error following cataract surgery?" the majority said PRK, with LASIK as the second most popular answer. We wondered about the greatest postoperative concern with LASIK and PRK, and the majority responded that it is refractive accuracy, followed by dry eye. Finally, when asked, "What new refractive technique are you most excited about?" the answers were fairly close. Riboflavin UV crosslinking was the most popular answer, followed by the SMILE technique and improved aberrometers.

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