Photorefractive keratectomy retreatments: comparison of two methods of excimer laser epithelium removal.

Abstract

Regression and undertreatment after initial photorefractive keratectomy (PRK) in higher myopes is not unusual. Patients frequently desire 20/20 uncorrected vision, which necessitates retreatments or enhancements. However, the safest and most efficacious way to treat these patients has not yet been established. This study evaluates two techniques of PRK enhancements, comparing two different methods of laser epithelial removal. Retrospective, nonrandomized, comparative trial. A total of 224 eyes. Eyes were identified that had 6-month follow-up after a PRK enhancement from February 1995 through February 1997. Two methods of treatment were identified. The same VISX 20/20B laser in the same clinic was used for all retreatments. Group I patients had a total removal of the epithelium in a mode phototherapeutic keratectomy (PTK) prior to the refractive ablation. Group II patients had a total laser epithelial removal in two steps prior to the refractive ablation. The first step was a PRK and then a PTK. The disappearance of epithelial fluorescence was the end point for the PTK ablation in groups I and II. There were 131 eyes in group I and 93 eyes in group II. The mean spherical equivalent (SE) prior to the original PRK in group I was -7.5 diopters (D) +/- 3 D and in group II was -7.75 D +/- 2.34 D. The mean SE prior to the PRK retreatment in group I was -2.22 D +/- 1.29 D and in group II was -1.89 D +/- 0.83 D. The mean postoperative 6-month SE after the PRK enhancement in group I was -0.05 D +/- 0.80 D and in group II was 0.01 D +/- 1.08 D. A greater proportion of group I eyes (7.8%) had arcuate haze and a hyperopic shift from the 1- to 6-month postoperative visit (P = 0.03). A two-step laser epithelial removal compared with a one-step PTK epithelial laser removal in PRK retreatments provides a more even and confluent epithelial removal, less risk of arcuate haze development, and less risk of a hyperopic shift from 1 to 6 months after the retreatment.