Influence of topical NPH-insulin use on wound healing and oxidative stress in alkali corneal burns: an experimental study in a rabbit model

Background: In acute alkali corneal burns, the routine treatment protocol includes suppressing inflammation using corticosteroids. In recent years, there has been a growing interest in the role of insulin in wound healing research due to its remarkable positive effects. Aims: The present study aimed to compare the healing effects of dexamethasone-the conventional approach- and NPH-insulin on alkali corneal burns. Methods: An alkali corneal burn was created using Ca (OH)(2) in all subjects. One group (n=6) was treated with an ophthalmic ointment containing dexamethasone (group I), and another group (n=6) was treated with an insulin ointment (group II). The control group (n=6) received no treatment (group III). Clinical changes in the corneal burn areas were monitored on days 3, 7, 14, and 21. The animals were euthanized on day 21. The excised corneas were examined for histopathological, immunohistochemical, and biochemical changes. Results: A more successful clinical recovery graph was drawn for group II. Particularly, a significant (P<0.05) improvement was detected in group II on day 21. The highest positivity in MMP-9 corneal staining was found in group I. Group II had a significant (P<0.05) increase in total antioxidant capacity (TAC) values. The treatment groups showed a significant (P<0.05) decrease in total oxidant content (TOC) values and a significant (P<0.05) increase in reduced glutathione (GSH) levels as compared with the control group. Conclusion: Topical NPH-insulin provided rapid and uncomplicated clinical recovery of alkali corneal burns. Insulin and dexamethasone showed similar effects like increased antioxidant molecules and decreased oxidant substances which indicated that insulin may prevent free radical formation in the cornea.