Protective role of oral antioxidant supplementation in ocular surface of diabetic patients.

AIM To investigate the effect of vitamin C and E supplementation in the levels of nitrite, nitric oxide (NO) related metabolite, and ocular surface parameters in diabetic patients. METHODS 50 patients with non-insulin dependent diabetes mellitus were given vitamin C (1000 mg/day) and vitamin E (400 IU/day) supplementation for 10 days. Nitrite levels in tears were measured by photometric determination before and after vitamin supplementation. Tear function parameters (Schirmer test I, BUT, ocular ferning test) and brush cytology analysis of the conjunctival epithelium were also evaluated. RESULTS Nitrite levels were found to be significantly reduced (p<0.05) after 10 days of vitamin C and E supplementation. Improved values for Schirmer test, BUT test, and ocular ferning test were also found. Goblet cell density and grading of squamous metaplasia showed a significant improvement. CONCLUSIONS Oxidative stress and free radical production are elevated in diabetes mellitus. Antioxidants, such as vitamin C and vitamin E, probably have an important role in reducing the oxidative damage produced by nitric oxide and other free radicals and improving the ocular surface milieu.