EFFECT OF OPTIC ZONE SIZE ON THE OUTCOME OF PHOTOREFRACTIVE KERATECTOMY FOR MYOPIA

Purpose: To determine the effect of optic zone size on the outcome of photorefractive keratectomy (PRK) for myopia. Setting: Department of O phthalmology, Samsung Medical Center, Seoul, Korea. Methods: Twenty pa tients, 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 o ther with a 6.0 mm diameter optic zone. An identical postoperative eye drop regimen was used. During the 6 month follow-up, changes in refrac tion, uncorrected visual acuity, and corneal anterior stromal haze wer e evaluated. At the end of the follow-up, patients completed a questio nnaire 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 w ith a 6.0 mm optic zone. Eyes with myopia over 6.00 D and a 6.0 mm opt ic zone had significantly faster recovery of uncorrected visual acuity at 2 and 12 weeks. There was no increased anterior stromal haze in th e 6.0 mm optic zone eyes, despite the deeper stromal ablation. Night-v ision problems were more prevalent in the 5.0 mm optic zone group, whi ch also had a greater incidence of ablation decentration. Conclusion: A 6.0 mm optic zone for myopic PRK seems to produce better outcomes. F urther evaluation of long-term results is needed.