PHOTOREFRACTIVE KERATECTOMY AND CATARACT

Fifty-male albino rabbits were studied. Ten animals sen ed as controls . Forty animals were prepared to receive photorefractive keratectomy ( PRK), including anesthesia, scraping of the corneal epithelial cells, etc. Twenty of these animals then received PRK with energy delivered b y excimer laser (pulse rate = 20 Hz, fluence 250 mJ/cm(2) number of pu lses = 6032; cumulative UV dose = 1508 J/cm(2)). The other 20 animals were exposed to the same operating microscope light as the PRK-treated animals, but they did not receive PRK. All three groups were divided into halves: the first half was immediately analyzed at 0 time, and th e second half was observed 1 year later. Samples of aqueous humor and lens were analyzed. The levels of reduced and oxidized glutathione, hy drogen peroxide, ascorbic acid, and malondialdehyde were determined. E xcimer laser-induced ultrastructural modifications of the lens, verifi ed through scanning electron microscopy, were studied at the same inte rvals. Immediately after PRK, the biochemical parameters studied, both in aqueous humor and in lens of treated animals, showed significant d ifferences. One year later, the observed biochemical variations in len s were still present, whereas aqueous humor values did not significant ly differ from control values. Ultrastructural abnormalities of the le ns appeared only 1 year after PRK. In the animals that received only t he preparation for PRK the biochemical and ultrastructural differences did not significantly vary as compared to the data obtained from cont rol animals. These findings suggest that the biochemical and ultrastru ctural lens alterations induced by PRK may represent events relevant t o cataractogenesis in the rabbit. (C) 1997 by Elsevier Science Inc. Al l rights reserved.