Effect of Different Treatment Regimen withDexamethasone and Acetylcysteine onCorneal Wound Healing in Rabbits

Background: the effect of corticosteroid therapy on cornealwound healing is controversial. the objective of this study wasto evaluate the effects of combination therapy with dexamethasoneand acetylcysteine at different times and durationson experimentally-induced corneal wounds and haze in rabbits.methods: eighteen adult new zealand white rabbits weredivided into three groups of six each. under anesthesia cornealwounds were created surgically in the center of all eyes. theright eyes of rabbits in group 1 were treated topically withacetylcysteine and dexamethasone immediately after surgery,those in group 2 were treated with acetylcysteine from day 1and with acetylcysteine and dexamethasone from day 8, andthose in group 3 were treated with acetylcysteine from day 1 andwith acetylcysteine and dexamethasone from day 15. the lefteyes were assigned as controls and were treated with normal saline.all eyes were treated six times a day for 28 days. cornealwounds were measured by fluorescein staining every day.results: the combination of acetylcysteine and dexamethasonein group 1 significantly increased mean healing time, but didnot change that in groups 2 and 3. clinical and histopathologicexaminations revealed that one month after the ulceration ingroups 1 corneal haze was greater in treated than in the controleyes. moreover, there was no significant difference between thecontrol and treated eyes of group 1, 2, or 3 in terms of cornealhaze at two or three months after the ulceration.conclusions: the findings of the present study show that theassociation of 3% concentration of nac and 0.1% concentrationof dexamethasone immediately after corneal ulcerationcan delay corneal wound healing, and consequently producemore corneal haze. thus, the use of 0.1% concentration ofdexamethasone should be delayed at least until the completionof the epithelial defects