5-YEAR RESULTS OF PHOTOREFRACTIVE KERATECTOMY FOR MYOPIA

Purpose: To evaluate the long-term stability, complications, and causa tive factors in eyes that had photorefractive keratectomy (PRK) for my opia. Setting: Kangnam St. Mary's Hospital, Seoul, Korea. Methods: Thi s study evaluated the results of PRK in 201 myopic eyes with a consecu tive 5 year follow-up. Preoperative myopia ranged from 2.25 to 12.50 d iopters (D), with astigmatism of less than 1.50 D. The excimer laser w as set to a maximum correction of -6.50 D at a 5.0 mm diameter ablatio n zone. Patients with more than 7.00 D of myopia had double-pass PRK w ith two different ablation zone sizes (5.0 and 4.5 mm). The data were statistically analyzed using polynomial regression for evaluating long -term stability and myopic regression and Cox's proportional hazard mo del for evaluating causative factors. Results: An uncorrected visual a cuity better than 20/25 was achieved in 62.4% of eyes. The main compli cation after PRK was myopic regression. Mean refractive error 5 years after PRK was -2.43 +/- 1.90 D. It was -1.49 +/- 0.60 D in moderately myopic eyes (less than 6.50 D) and -3.55 +/- 2.31 D in highly myopic e yes (over 7.00 D). According to our evaluation, the possible causative factors for myopic regression were pre-PRK refraction (P < .0001) and post-PRK corneal haze (P = .01); their relative risks were 3.33 and 1 .93, respectively. Multivariate analysis eliminated the corneal haze f actor. Conclusion: Myopic regression occurred as long as 5 years after PRK, with the most important factor for myopic regression being pre-P RK refraction.