| Objective To investigate the effect of free oxygen radical in the rabbit cornea apoptosis-induced corneal wound healing respone after pholorefractive keratectomy and the influence of topical antioxidants Vitamin C, Vitamin E on cornea tissue having undergone PRK.Methods 28 rabbits were divided 3 groups, 4 rabbits served as controls and the others served as experimental rabbits which were divided 2 groups, each consisting of 12 animals. They were underwent bilateral photorefractive keratectomy with 193nm argon fluoride excimer laser to correct 5 diopters of myopia. Following treatment, one groupthe left eye of each rabbit was subconjunctival injection with Vitamin C 0.1 every day.The right eye served as control. The other group the left eye of each rabbit wassubconjunctival injection with Vitamin E 25mg every day. The right eye served as control.Rabbits were killed at 1,3,7 and 14 days respectively, then measured the activity of corneal superoxide dismutase(SOD) with xanthine oxidase method and glutathioneperoxide(GPx) with modified glutathione, the level of corneal malondialdehyde(MDA) with barbituric acid reaction. At the same time, corneas were prepared for H.E.staining to observe histopathological changes and the quantities of corneal stroma cells after PRK. Corneal cell apoptosis was evaluated by terminal deoxyribonucleotidyl transferase mediated deoxyuridine triphosphate nick end labeling (TUNEL) to detect DNA fragmentation.Results (1) It was found that significant decrease in SOD, GPx activity (P<0.05) and increase in MDA level (P<0.05) compared with the control following 1,3 days after PRK. But the corneal SOD, GPx activity in effect of antioxidants group is significant higher than that of PRK group (P<0.05). The level of MDA in effect of antioxidants group is significant lower than that of PRK group (P<0.05). (2) Apoptosis was detected remarkably in anterior keratocytes from 1 day to 14 days (P<0.01). The level of keratocyte apoptosis in effect of antioxidants group less then PRK group (PO.05). (3) The number of keratocytes were increased after operation. The level of proliferation in effect of antioxidants group less then PRK group (P<0.05).Conclusions The presence of free oxygen radical mediated tissue damage in the cornea with lipid peroxidation following excimer laser keratectomy. They may contribute to an increase apoptosis in cornea after PRK. The topical application of antioxidants Vitamin C or Vitamin E can decrease corneal oxygen radical tissue damage after excimer laser keratectomy, inhibiting keratocyte apoptosis, preventing the over-proliferation andall of them may reduce postoperative corneal haze and regression.
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