INTRASTROMAL EPITHELIAL ACCRETION FOLLOWS DEEP EXCIMER ANNULAR KERATECTOMY

The purpose of this study was to evaluate corneal reepithelialization and wound healing following annular excimer keratectomy. Two sets of e xperiments were performed on 35 rabbit eyes. In the first set of exper iments, experiment I, deep Fresnel excimer keratectomy was performed, with a 6-mm outer and 3-mm inner diameter. Animals were sacrificed at 1, 5, 12, and 16 weeks, and corneas were examined by light and electro n microscopy. In experiment II, the central epithelium was left intact , and superficial and deep mid-peripheral excimer annular keratectomie s were performed measuring 6 mm in outer and 3 mm in inner diameter. A nimals were sacrificed at 1 week, and corneas were examined by light m icroscopy. Following deep Fresnel excimer keratectomy (experiment I), corneas showed stromal edema in the central 3-mm zone. Intrastromal is lands of epithelial cells with PAS positive basement membrane-like str uctures were seen histologically at 1 week. Electron microscopy showed loss of stromal collagen in areas adjacent to epithelial islands; in areas distant from the epithelial islands, the stromal collagen appear ed normal. The overlying central stroma sloughed after 5 weeks. Anteri or stromal scarring was observed. In experiment II (mid-peripheral ann ular keratectomy), intrastromal epithelial accretion was present in co rneas with deep annular keratectomy but not in superficial annular ker atectomy. Intrastromal epithelial accretion follows deep excimer annul ar keratectomy and is associated with adjacent stromal degradation.