Objective: To study the histologic changes in rabbit corneas after photo-therapeutic keratectomy (PTK), define the indications and treatment parameters and evaluate efficacy of PTK.
Methods: (1) The model of superficial corneal scar in rabbit was made by burn with 8.17% sulfuric acid, and then treated with PTK in two weeks. The corneas were examined with confocal microscope in vivo, nerve staining, light and transmission electron microscope during period after PTK to study the histopathologic changes. (2) Thirty eyes with superficial corneal diseases including 12 eyes with corneal dystrophy, 2 eyes with band degeneration, 10 eyes with scar after infection and trauma and 6 eyes with Dimmer nummular keratitis were treated with PTK. The method of treatment was varied with different diseases. Follow-up was more than six months. To investigate the change of haze, visual acuity, refraction and keratometric power during period after PTK, chi-square tests were used.
Results: (1) Experimental group: in the ablative zone at early time after PTK, there were infiltration of polymorphonuclear leukocytes accompanied by macrophages, proliferation of fibroblast and loose nascent collagen in disorder in the anterior stroma. The wound healing process was stable at six months after PTK. (2) Clinical group: compared with the preoperative visual acuity, the best corrected visual acuity was improved in 21 eyes (70.0%), unchanged in 5 eyes (16.7%) and decreased in 4 eyes (13.3%) at six months after PTK, and the results were better for corneal dystrophy and band degeneration. Haze grade 0.5 was in five eyes, grade I in two eyes and grade 0 the rest. The mean hyperopic shift was + 1.52 D.
Conclusions: The wound healing process in rabbit cornea stabilizes at six months after PTK. PTK is a simple, safe, effective treatment for superficial corneal diseases. The indications for PTK are corneal pathology in the anterior one-third of the cornea, especially corneal dystrophy and band degeneration.