A Comparative Study for Apoptosis on the Degree of the Amount of Photorefractive Ablation in Photorefractive Keratectomy

ABSTRACT

PURPOSE: This study was aimed to evaluate changes in the stromal keratocyte after ablation of 50 micrometer and 100 micrometer with use of photorefractive keratectomy(PRK). METHODS: At 4 hours, 24 hours, 72 hours, 7 days and 1 month after PRK, each group of rabbits including normal control group was treated with terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labeling(TUNEL) staining using ApopTag(R) kit in vivo, then apoptotic keratocytes were evaluated with light microscope. RESULTS: There was no response with TUNEL staining of the epithelial cells, stromal keratocyte, and endothelium in normal cornea. In the ablation group, however, regardless of the depth of photorefractive ablation, the TUNEL signal was maximal after 4 hours, and it decreased with time. The signal was more intense in 100 micrometer ablation group than 50 micrometer ablation group, although the signal was not observed at the endothelial cells in both groups. The number of apoptotic stromal keratocytes at each time point of 4 hr, 24 hr, 72 hr, and 1 week was 57+/-8.9, 49+/-7.5, 36+/-5.1, and 12+/-1.3 cells/field in 100 micrometer ablation group, and 31+/-4.4, 28+/-4.6, 21+/-3.9, and 5+/-1.1 cells/field in 50 micrometer ablation group, and the difference between the two groups was statistically significant(P<0.05). CONCLUSION: The more the amount of ablation with photorefractive keratectomy, the stronger the apoptotic response. The postoperative apoptotic response was observed especially within 1 week. These findings suggest that early suppression of postoperative apoptosis within 1 week will influence on the prognosis of visual quality after photorefractive keratectomy, and more studies will be needed in the future.