Confocal Microscopic and Histopathologic Changes in Corneal Morphology Under Corneal Scraped Injury in Rabbit

PURPOSE: To investigate that the effects of early wound healing stage after corneal epithelial scrape injury. METHODS: We studied the change of scraped corneal wound like corneal cells, corneal thickness, acelluar zone, and celluar morphology occurring at the time points of 1, 4, 12, 24, 48, 72 hours, and 7 days after corneal epithelial scrape injury by the confocal microscopy and EM findings in 4 each group rabbits. RESULTS: By normal confocal microscopy, the mean cell density was 891 cells/mm2 in the anterior stroma and decreased to 814 cells/mm2 in the middle stroma, 731 cells/mm2 in the posterior stroma, and the endothelial density was 3236 cells/mm2. The change in the morphology of the keratocyte nuclei from an elliptical shape anteriorly, to a more elongated shape posteriorly. Apoptosis revealed like as condensation or fragmentation of chromatin and nuclei, vesicle formation, apoptotic bodies after corneal scraped injury by EM findings. The mean thickness of normal cornea was as follow; 47 micrometer in the epithelium, 334 micrometer in the stroma, and 392 micrometer in total cornea. The thickness of postoperative cornea including stromal thickness and total thickness increased at the early wound healing stage, and then decreased to the postoperative 48 hours(P<0.001). Mean range of acellular zone in the stroma increased at the early wound healing, but significantly decreased at the postoperative 48 hours, 79 micrometer(P<0.001). CONCLUSIONS: Keratocyte cell density and corneal thickness at the three portions of cornea, the thickness of stromal acelluar zone, and the changes of cellular morphology were related with a kind of the early post-inflammatory reaction, especially 24 hours, of corneal scraped injury. It should be needed more studies concerned with control of early post-inflammatory reaction.

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

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.