RESUMO
BACKGROUND: Photorefractive keratectomy for myopia can be performed using an expanding or contracting iris diaphragm, either of which allows for greater ablation centrally and less tissue ablation toward the edge of the treatment zone. METHODS: To compare the effects of these two strategies, eight rabbits underwent bilateral 5.00-diopter myopic ablations, performed with a contracting diaphragm in one eye and an expanding diaphragm in the other. RESULTS: The rate of epithelial healing and degree of anterior stromal haze, monitored by a masked observer, were similar for the two groups, as was the amount of corneal flattening. CONCLUSIONS: These results in rabbit corneas do not suggest a particular advantage of either the expanding or contracting apertures for achieving central corneal flattening in photorefractive keratectomy.
Assuntos
Córnea/fisiologia , Iris/fisiologia , Terapia a Laser , Miopia/cirurgia , Cicatrização/fisiologia , Animais , Lesões da Córnea , Epitélio/fisiologia , CoelhosRESUMO
PURPOSE: Superficial corneal ablation using the 193 nm excimer laser for the correction of myopia and astigmatism produces histologic changes in the corneal profile that can be quantitatively analyzed. METHODS: Using the excimer laser, spherical and cylindrical corneal ablations were performed on rabbit eyes at depths of 2, 4, 6, and 8 diopters. After 12 weeks, the corneas were examined histologically using a dichlorotriazinyl aminofluorescein stain for collagen, and the results were quantified using a digital video image analysis system. RESULTS: Epithelial thickness and thickness of new collagen were positively correlated with the depth of ablation after spherical ablations. With astigmatic ablations, epithelial thickness and new collagen production were correlated with ablation depth in one axis only. CONCLUSION: These results suggest that during cylindrical corneal ablations with the excimer laser, radially asymmetrical stromal ablations produce quantitatively asymmetrical wound healing.
