EyeWorld Asia-Pacific June 2014 Issue

51 EWAP rEfrActivE June 2014 PRK vs. LASIK updated by rich Daly EyeWorld Contributing Writer the latest research indicates the two leading photorefractive approaches provide similar outcomes, but specific circumstances can give one advantages over the other R efractive laser patients can derive similar visual results from LASIK and photorefractive keratectomy (PRK), according to the latest side-by-side comparison, which may assure surgeons that they can switch between the procedures as patient circumstances dictate. LASIK and PRK are comparably safe, effective, and predictable procedures for excimer laser correction of high astigmatism greater than 3 D in myopic eyes, concluded a recent study in the Journal of Refractive Surgery. 1 The study by Lars Wagenfeld, MD , University Medical Center Hamburg-Eppendorf, Hamburg, Germany, and colleagues retrospectively analyzed up to 6 months of postop surgical results in 114 consecutive randomly selected myopic eyes (up to –8.63 D spherical equivalent for LASIK and –8.38 D for PRK) with astigmatism of greater than 3 D (up to –5.75 D cylinder for both LASIK and PRK). Patients who were evenly divided between PRK and LASIK had no statistically significant difference in efficacy, safety, or predictability. Vector analysis of the cylindrical correction found no statistically significant difference in the surgically induced astigmatism, although the correction index showed a slight and significant advantage of LASIK over PRK. The findings of Dr. Wagenfeld and colleagues echo the recent experience of Vance Thompson, MD , assistant professor of ophthalmology, Sanford School of Medicine, University of South Dakota, Sioux Falls, SD, U.S. An original investigator in the FDA-monitored studies for PRK and LASIK in the 1990s, Dr. Thompson said both leading types of photorefractive surgery continue to provide good results. “I highly respect PRK and LASIK and have seen a lot of good from each, but over the years have seen complications from each, too,” Dr. Thompson said. “What I like about this study is that it supports the philosophy that in general if a patient is a good candidate for LASIK they are also a good candidate for PRK, even high myopic and/or astigmatic corrections. The reverse is not true though. There are many patients who are not candidates for LASIK who can safely undergo PRK.” One key to avoiding complications is selecting the best procedure for each patient. The first step is assessing the patient’s corneal thickness and corneal topographic regularity. Patients with normal topography anteriorly and posteriorly, who do not rub their eyes and who would have more than 300 μm of residual corneal stroma after a 110-μm femtosecond flap and laser ablation are typically good LASIK (or PRK) candidates, he said. In cases of thinner corneas, anterior basement membrane dystrophy, and when activity- related trauma can be an issue, Dr. Thompson prefers PRK. “With anterior basement membrane dystrophy, PRK can be a great way to both treat the refractive error and re-establish a more normal epithelial adherence and regularity,” Dr. Thompson said. “If you want to treat both the refractive error and the anterior basement membrane dystrophy, you have to make sure that the preoperative measurements are accurate enough for PRK. Otherwise, it is better to do a corneal scraping or PTK, allow things to heal really well, then get accurate measurements and do the refractive correction.” Concerns that arise with either procedure include dry eye. Dr. Thompson avoids any refractive procedure in patients with epithelial staining. “I would consider this a stressed corneal surface and a setup for wound-healing issues,” he said. Anterior basement membrane dystrophy case where PRK or PTK can re-establish a more normal epithelial regularity and adherence Source: Vance Thompson, MD continued on page 53