RETREATMENT FOR SIGNIFICANT REGRESSION AFTER EXCIMER-LASER PHOTOREFRACTIVE KERATECTOMY - A PROSPECTIVE, RANDOMIZED, MASKED TRIAL

Purpose: Regression, a gradual partial or complete return to the myopi c state, remains a common complication of excimer laser photorefractiv e keratectomy (PRK) and limits the predictability of refractive outcom e, especially in high myopia. An estimated 10% to 20% of patients, the refore, request a repeat PRK procedure, This study was designed to pro vide patient selection criteria and guidelines for successful retreatm ent. Methods: One hundred six patients who had regressed were randomiz ed to 1 of 4 retreatment groups comprising (1) those with minimal haze after their first PRK who received an exact retreatment; (2) those wi th minimal haze treated with a 50% deliberate overcorrection; (3) thos e with significant haze (greater than or equal to 2+ haze) given an ex act retreatment; and (4) those with significant haze who received a 50 % overcorrection, A Visx 20/20 laser was used in each case. Mean follo w-up after retreatment was 12 months (range, 6-18 months). Results: De liberate overcorrection (groups 2 and 4) resulted in a statistically s ignificantly better refractive outcome (P = 0.026 at 6 months). Analys is of variance showed that significant haze after the first PRK was th e most important predictor of a poor outcome after retreatment, other factors being high original myopia, marked regression, and loss of bes t-corrected visual acuity. Conclusions: A retreatment PRK procedure fo r significant regression will reduce residual myopia significantly in the majority of patients, and a deliberate overcorrection (50%) reduce s the chance of further regression. However, patients with high myopia who have regressed beyond approximately -3.50 diopters originally and who show significant anterior stromal haze (>2+) should be retreated only with great caution, because of the risk of further regression, ha ze, and loss of visual acuity.