Effect of optic zone size on the outcome of photorefractive keratectomy for myopia

Abstract

Purpose: To determine the effect of optic zone size on the outcome of photorefractive keratectomy (PRK) for myopia.Setting: Department of Ophthalmology, Samsung Medical Center, Seoul, Korea.Methods: Twenty patients, 10 with myopia under 6.00 diopters (D) and 10 with myopia over 6.00 D, had bilateral PRK with identical dioptric corrections in both eyes. One eye was treated with a 5.0 mm diameter optic zone and the other with a 6.0 mm diameter optic zone. An identical postoperative eyedrop regimen was used. During the 6 month follow-up, changes in refraction, uncorrected visual acuity, and corneal anterior stromal haze were evaluated. At the end of the follow-up, patients completed a questionnaire on night-vision disturbance, foreign-body sensation, tenderness, and preference.Results: Two weeks postoperatively, eyes with a 5.0 mm optic zone had a significantly greater hyperopic shift than those with a 6.0 mm optic zone. Eyes with myopia over 6.00 D and a 6.0 mm optic zone had significantly faster recovery of uncorrected visual acuity at 2 and 12 weeks. There was no increased anterior stromal haze in the 6.0 mm optic zone eyes, despite the deeper stromal ablation. Night-vision problems were more prevalent in the 5.0 mm optic zone group, which also had a greater incidence of ablation decentration.Conclusion: A 6.0 mm optic zone for myopic PRK seems to produce better outcomes. Further evaluation of long-term results is needed.