ANTIOXIDANTS REDUCE CORNEAL LIGHT-SCATTERING AFTER EXCIMER KERATECTOMY IN RABBITS

Background and Objective: Excimer laser-corneal tissue interaction liberates highly reactive free radicals. Our aim was to determine if intraoperative application of antioxidants reduces the postoperative corneal light scattering by minimizing free radical-mediated cellular injury. Study design/materials and methods: Phototherapeutic keratectomy (PTK) was performed in 20 rabbit eyes. Following 40-mu m epithelial ablation, rabbits were divided into two groups and received 1-minute intraoperative application of either 50% dimethyl sulfoxide and 1% superoxide dismutase or vehicle (balanced salt solution) only. This was followed by a 6-mm diameter 100-mu m PTK. Corneal light scattering was measured for 18 weeks using scatterometry. A Light scattering index (SI) ranging from 0-10 was calculated; SI = 1 represents normal scattering. Light microscopic examination was performed in selected corneas. Results: The mean baseline SI was similar for both groups (P = 0.95). Corneal haze followed a pattern of gradually increasing to peak at 23 weeks, and regressing partially thereafter. The decrease in mean SI following antioxidant application (dimethyl sulfoxide and superoxide dismutase) as compared to control group approached significance at 3 weeks (0.1 > P > 0.05) and was highly significant at 9 weeks (P < 0.05). Conclusion: Intraoperative application of antioxidants decreases light scattering following excimer keratectomy in rabbit corneas. UV-induced free radicals may play a role in the pathogenesis of corneal Light scattering following excimer laser keratectomy. (C) 1995 Wiley-Liss, Inc.