Mitomycin-C concentration in cornea and aqueous humor and apoptosis in the stroma after topical mitomycin-C application - Effects of mitomycin-C application time and concentration

Purpose: To evaluate the effects of the applied mitomycin-C (MMC) concentration and application time on the aqueous MMC concentration and apoptosis in the corneal stroma. Methods: New Zealand white rabbits underwent mechanical epithelium debridement of the central 7.5 mm of the cornea. A sponge soaked in MMC solution was placed on the denuded corneal stroma. The effect of the exposure times ranging from 15 to 120 seconds and the different MMC concentrations ranging from 0.005% to 0.04% on the aqueous MMC concentration and the apoptosis in the stromal cells were evaluated. Results: The aqueous concentration of MMC increased linearly with increasing exposure time and MMC concentration. The correlation between the aqueous MMC concentration and the applied concentration (r = 0.809, P < 0.001) was higher than the correlation between the aqueous MMC concentration and the application time (r = 0.693, P < 0.001). Terminal deoxyribonucleotidyltransferase-mediated dUTP-digoxigenin nick end labeling (TUNEL)-positive cells were detected in the superficial stroma of the central denuded cornea. The numbers of TUNEL-positive cells increased linearly with increasing concentrations, and the increase was statistically significant (P = 0.026). However, the numbers of TUNEL-positive cells increased only slightly with an increasing application time, and the increase was not statistically significant (P = 0.928). Conclusions: Reducing the applied concentration or decreasing the exposure time might be a good modality for reducing the potential MMC toxicity. The applied MMC concentration had greater effects on the aqueous MMC concentration and apoptosis in the stromal cells than the exposure time.