Antioxidants reduce corneal light scattering after excimer keratectomy in rabbits

Abstract

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-microns 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-microns 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 2-3 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.