One-year results of PRK in low and moderate myopia: fewer than 0.5% of eyes lose two or more lines of vision.

Abstract

To retrospectively evaluate the results of myopic photorefractive keratectomy (PRK) for different levels of intended correction, including analysis of loss of best spectacle-corrected visual acuity. Four hundred seventy-five consecutive eyes with 1 year of follow-up that had PRK for the correction of 1-7 diopters (D) of myopia by using the Summit SVS Apex excimer laser. Three hundred forty-eight eyes were examined at 1 year. This study was confined to the 236 eyes with 1 year of follow-up that had PRK without astigmatic keratotomy. Eyes also were analyzed according to the range of attempted correction (0-3 D, low; 3.1-6D, moderate; and > or =6.1 D, high moderate). Manifest refraction, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), surface regularity index (SRI), and surface asymmetry index (SAI) were evaluated for each group. One year after PRK, 91% of all eyes were within 1 diopter and 73% of eyes were within 0.5 diopter of emmetropia. Uncorrected visual acuity was 20/25 or better in 79% and 20/40 or better in 96% of eyes. Two lines of BSCVA were lost in only 0.4% of eyes (one of 236). No eye lost >2 lines of BSCVA, and 30% gained one line. Mean SRI and SAI were increased as compared with preoperative values, but were within the normal range for our patient population (ranges, 0.2-1.0 and 0.1-0.7, respectively). UCVA, BSCVA, and predictability decreased, whereas SAI and SRI increased, with increasing attempted correction. PRK effectively reduced myopia in all eyes with 12 months' follow-up. Predictability tended to decrease with increasing attempted correction, even for low to moderate myopia. PRK may induce mild surface asymmetry and irregularity, and these alterations tend to increase with higher attempted correction. Fewer than 0.5% of eyes lost > or =2 lines of best-corrected visual acuity.