Effect of Cysteine in Transgenic Mice on Healing of Corneal Epithelium after Excimer Laser Photoablation

Purpose: To evaluate the role of prepared cysteine per os in corneal epithelial healing in transgenic mice (B6(A)-Rpe65rd12/J) after excimer laser photoablation. Materials and Methods: In our prospective case series, 60 eyes of 30 mice had uneventful bilateral excimer laser photoablation. A first group, composed of 15 mice, received standard topical post-operative therapy with tobramycin, diclofenac and dexamethasone eyedrops, pluscysteine 5 mg 5 μg/10 μl phosphate-buffered saline (3 times a day for 1 week) per os or until corneal re-epithelialization was complete. The control group of 15 mice received standard post-operative therapy plus placebos. The mice were monitored daily, commencing the day after surgery, for 7 days to evaluate the corneal re-epithelialization rate using a video slit-lamp camera with a cobalt blue light. The mean diameters of corneal wounds were measured. Videotaped images were recorded and analysed by computer planimetry. Results: All the eyes of the mice treated withcysteine healed completely by day 5 after surgery, with a mean re-epithelialization time of 92 ± 10 h (SD); the mean re-epithelialization time was 125 ± 8 h in eyes that received the placebo. There were no statistically significant differences between the 2 groups in corneal haze presentation during follow-up, perhaps because the time period was too brief (7 days). However, corneal clarity in the study group was greater than in the control group, as shown on slit-lamp biomicroscopy. No side effects or toxic effects were documented. Conclusions: These data suggest that cysteine significantly accelerates epithelial healing after excimer photoablation. A further clinical study should be performed to confirm the results obtained in this study, and the long-term efficacy of cysteine in preventing corneal haze.