effect of different treatment regimen with dexamethasone and acetylcysteine on corneal wound healing in rabbits

background: the effect of corticosteroid therapy on corneal wound healing is controversial. the objective of this study was to evaluate the effects of combination therapy with dexametha-sone and acetylcysteine at different times and durations on experimentally-induced corneal wounds and haze in rabbits. methods: eighteen adult new zealand white rabbits were divided into three groups of six each. under anesthesia corneal wounds were created surgically in the center of all eyes. the right eyes of rabbits in group 1 were treated topically with acetylcysteine and dexamethasone immediately after surgery, those in group 2 were treated with acetylcysteine from day 1 and with acetylcysteine and dexamethasone from day 8, and those in group 3 were treated with acetylcysteine from day 1 and with acetylcysteine and dexamethasone from day 15. the left eyes were assigned as controls and were treated with normal saline. all eyes were treated six times a day for 28 days. corneal wounds were measured by fluorescein staining every day. results: the combination of acetylcysteine and dexamethasone in group 1 significantly increased mean healing time, but did not change that in groups 2 and 3. clinical and histopathologic examinations revealed that one month after the ulceration in groups 1 corneal haze was greater in treated than in the control eyes. moreover, there was no significant difference between the control and treated eyes of group 1, 2, or 3 in terms of corneal haze at two or three months after the ulceration. conclusions: the findings of the present study show that the association of 3% concentration of nac and 0.1% concentration of dexamethasone immediately after corneal ulceration can delay corneal wound healing, and consequently produce more corneal haze. thus, the use of 0.1% concentration of dexamethasone should be delayed at least until the completion of the epithelial defects.