Differences in Keratocyte Apoptosis Between Laser and Mechanical Removal of Corneal Epithelium for PRK in Rabbits

ABSTRACT

PURPOSE: To evaluate the effects of different corneal epithelial manipulations in PRK procedure on keratocyte apoptosis. METHODS: Rabbit cornea was examined qualitatively and quantitatively after epithelial scraping(Group I), epithelial scraping followed by PRK(Group II) and transepithelial PRK(Group III). Each of them were compared with that of unwounded control. RESULTS: The number of anterior stromal keratocytes had decreased significantly and TUNEL-positive cells were significantly increased in the anterior stroma in group I and group II on POD 3 days compared with control group(p<0.05). There was a statistically significant increase in the number of anterior stromal keratocytes in group II compared with group III on POD 1 month(p<0.05). In group I and II, keratocytes that had morphologic changes consistent with apoptosis were detected with transmission and scanning electron microscopy on POD 3 days. But in group III, there were many normal appearing keratocyte in the anterior corneal stroma, and few keratocytes undergoing apoptosis. CONCLUSIONS: Transepithelial PRK induced lower levels of keratocyte apoptosis in rabbit cornea compared to those induced from epithelial scraping followed by PRK. This suggests that transepithelial PRK could be useful in preventing or minimizing refractive regression and corneal opacity, especially in cases of myopia or retreatment after regression.