ENLARGEMENT OF THE PHOTOREFRACTIVE KERATECTOMY OPTICAL ZONE

Purpose: To evaluate the safety and efficacy of a photorefractive kera tectomy (PRK) re-treatment procedure that enlarges the optical zone an d treats undercorrection. Setting: Rotterdam Eye Hospital and Medisch Centrum Alkmaar, The Netherlands. Methods: This study evaluated 16 eye s that had PRK for myopia with the Summit excimer laser that resulted in a mean undercorrection of -2.82 diopters (D). Patients also reporte d impaired night vision including difficulty in driving, halos, and st ray light and ghost images. These phenomena persisted after spectacle correction of residual refractive error, necessitating further treatme nt with a larger ablation zone. With a VISX 20/20 excimer laser, the o ptical zone was enlarged to 6.0 mm and undercorrection treated with a 6.0 mm ablation. Results: At 13.5 months after re-treatment, mean redu ction in myopia was 1.70 D, resulting in a residual undercorrection of -1.08 D. In seven eyes, final refraction was within 1.00 D of emmetro pia. Only two patients continued to report night-driving problems. Con clusions: Re-treating undercorrections combined with enlarging the abl ation zone resulted in a reduction in myopia from a mean of 2.82 to 1. 08 D. Subjective reports of halos and stray light images were decrease d in all cases.