Five year results of photorefractive keratectomy for myopia

Abstract

PURPOSE: To evaluate the long-term stability, complications, and causative factors in eyes that had photorefractive keratectomy (PRK) for myopia. SETTING: Kangnam St. Mary's Hospital, Seoul, Korea. METHODS: This study evaluated the results of PRK in 201 myopic eyes with a consecutive 5 year follow-up. Preoperative myopia ranged from 2.25 to 12.50 diopters (D), with astigmatism of less than 1.50 D. The Excimer laser was set to a maximum correction of -6.50 D at a 5.0 mm diameter ablation zone. Patients with more than 7.00 D of myopia had double-pass PRK with 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 model for evaluating causative factors. RESULTS: An uncorrected visual acuity better than 20/25 was achieved in 62.4% of eyes. The main complication 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 eyes (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 factor. CONCLUSION: Myopic regression occurred as long as 5 years after PRK, with the most important factor for myopic regression being pre-PRK refraction.