Histopathological Finding of Cornea after Collagen Cross-Linking Using Riboflavin and Ultraviolet A in Rabbit

Purpose: To evaluate the histopathological changes of the cornea in rabbit corneas after accelerated collagen cross-linking. Methods: Right eyes of 7 adult New Zealand albino rabbits weighing 1.5 to 2.0 kg were studied. Right eyes of all animals were in the treatment group and left eyes were in the control group. The epithelium of all right eyes was removed and was crossed-linked with riboflavin 0.1% solution (10 mg riboflavin-5-phosphate in 10ml 20% dextran-T-500) applied every 3 minutes for 30 minutes, and exposed to UVA (360 nm, 3 mW/cm2) for 10 minutes. All rabbits were humanely euthanized and examined histologically. Apoptosis was evaluated using TUNEL staining. Results: There was a significant difference in the mean percent of apoptotic cells in the treated and control groups. In both keratocyte and endothelial cells of the treated cornea, the number of apoptotic cells was significantly higher than the control group. In the evaluation of cornea totally (endothelial and keratocyte), the mean percent and standard deviation of apoptotic cells were 18.29 ± 3.2 in right eyes and 6.29 ± 1.7 in left eyes. In the evaluation of apoptosis in keratocytes separately, the mean percent and SD in right eyes were 15.29±2.56 that was significantly higher in comparison with the left eyes 5.71±1.5. The mean and SD of apoptotic endothelial cells in right and left eyes were 2.86±1.07, 0.53±0.43, respectively, that were statically significant (P= 0.026). Conclusion: Although CXL is a safe procedure to arrest progression in keratoconus disease, due to endothelial cell damage in our study and others, there are some risks for endothelial cell damage and related complications; so, it needs for more studies.