CORNEAL EPITHELIAL RECOVERY FOLLOWING PHOTOREFRACTIVE KERATECTOMY

Aims-To further understand the morphological and functional recovery o f corneal epithelium following excimer laser photorefractive keratecto my (PRK). Methods-The right eyes (group 1) of 15 male, New Zealand whi te rabbits weighing 2-3 kg underwent PRK. The left eye of each rabbit (group 2) underwent simple mechanical de-epithelialisation and were ex amined as treated controls. Both eyes of another eight rabbits (group 3) served as untreated controls. All eyes underwent a corneal epitheli al permeability study by fluorophotometry at 2, 4, and 8 weeks after s urgery. Five animals in groups 1 and 2 were sacrificed at 9, 10, and 1 2 weeks after surgery. The animals in group 3 were sacrificed at the e nd of the 12 week experimental period. Both eyes of each sacrificed an imal were enucleated immediately and processed for both haematoxylin a nd eosin stain and electron microscopic study. The electron micrograph was magnified to 14 000x and the extent of hemidesmosome formation wa s quantified and analysed. Results-The corneal epithelial barrier to s odium fluorescein was subnormal and returned to a normal barrier state 4 weeks after PRK in group 1 whereas it was normal in group 2 through out the examination period. The extent of hemidesmosome formation was abundant yet subnormal in both groups 1 and 2 up to 12 weeks, when com pared with that in group 3. Conclusion-The corneal epithelium regained its functional barrier 4 weeks after PRK in rabbits while the extent of hemidesmosome formation was still subnormal 12 weeks after mechanic al de-epithelialisation, with or without PRK.