Abstract
Purpose: :
Mitomycin C (MMC) is frequently used after excimer laser keratectomy to avoid haze formation promoting keratocyte apoptosis. This could have adverse consequences if there is a very delay re–population of the cells in the cornea. Here, we evaluate, in a rabbit model, the effect of different concentrations and time of exposure in order to determine the ideal exposure time for different depths of ablation.
Methods: :
Photorefractive keratectomy (PRK) was performed in 25 rabbit eyes. After 40 µm epithelial ablation, a six–millimeter diameter 100µm deep PRK was performed. Animals were then divided into 5 groups. In group 1, a 6 mm circular sponge soaked with MMC (Group 1A 0.2mg/ml, 0.02%, Group 1B 0.4 mg/ml, 0.04%) was applied to the cornea for 15 seconds. In Group 2, a 6 mm circular sponge soaked with MMC (Group 2A 0.02%; Group 2B 0.04%) was applied to the cornea for 30 seconds. In Group 3, a 6mm circular sponge soaked in MMC (Group 3A 0.02%; Group 3B 0.04%) was applied for 1 minute. In Group 4, a circular sponge soaked in MMC (Group 4A 0.02%; Group 4B 0.04%) was applied for 2 minutes. Controls received vehicle only (Group 5). Corneal light scattering was measured weekly from 1 to 8 weeks. After 2 months, all rabbits were humanely euthanized and immunohistochemical analysis of the corneas was performed using TUNEL, α–SMA, Ki–67, anti–collagen III, V, VI and corneal stromal matrix glycosaminoglicans markers.
Results: :
A statistically significant decrease in mean light scattering was observed in all groups treated with MMC compared with controls. At 6–8 weeks no statistical differences in the light scatter index was observed between Groups 1 to 4. There was a strong correlation between the exposure time to MMC and the reduction in the central corneal of keratocyte population. However, no differences in myofibroblasts transformation were observed comparing different MMC concentrations or time exposures.
Conclusions: :
Controlled application of a low concentration (0.04%) and minimum exposure time (15 seconds) of MMC appears to be safe and effective to reduce corneal light scattering and inhibit myofibroblast transformation after a 100 µm deep photorefractive keratectomy in this rabbit model.
Keywords: cornea: stroma and keratocytes • refractive surgery: PRK • refractive surgery