RESUMO
OBJECTIVE: To examine the role of inflammatory cell invasion and aspects of tissue reaction on refractive regression and corneal haze after myopic PRK in rabbits. METHODS: Measurements were made for 12 weeks postoperatively of haze intensity, corneal topography, tear cytology, inflammatory cell invasion, subepithelial fibroblast density, and the thickness of the newly laid down connective tissue and of the regrown epithelium. RESULTS: Inflammatory cell invasion could be prevented by fitting a soft contact lens, but this had no effect on the haze or the regression. Haze intensity correlated with subepithelial fibroblast proliferation but not with new connective tissue formation or epithelial hyperplasia. Neither connective tissue nor epithelium regrew in the form of a lens and thus they could not account for regression. Intensive treatment with corticosteroids resulted in a marked reduction in postoperative haze and a slight lessening of long-term regression. Correspondingly, it reduced fibroblast proliferation. CONCLUSIONS: Haze appears, at least in part, to be a result of fibroblast proliferation. Regression is possibly caused by slow distortion of existing tissue rather than the growth of new.