Purpose: This study was designed to evaluate the effect of antioxidant supplementation on diabetic retinopathy (DR) over a 5-year follow-up period. To our knowledge, this is the first such clinical trial performed.
Methods: We recruited 105 type 2 diabetic patients with nonproliferative DR. A complete ophthalmic checkup and a plasma determination of oxidative (malonyldialdehyde [MDA]) and antioxidant parameters (total antioxidant status [TAS]) were obtained as the baseline. One part of the cohort was randomly assigned to oral antioxidant supplementation at nutritional doses. The same examinations were performed with 97 diabetic patients who completed the 5-year follow-up period. The best-corrected visual acuity, DR score, MDA, and TAS values were compared at the beginning and the end of the follow-up.
Results: Best-corrected visual acuity did not change during the follow-up, irrespective of supplementation. However, the retinopathy stage showed a retardation of progression in the subgroup with supplementation, but worsened in the subgroup with no antioxidant supplementation. Furthermore, the antioxidant supplementation group maintained its antioxidant plasma status levels, which was related to decreased oxidative plasma activity.
Conclusions: Oral antioxidant supplementation could be a useful adjunctive long-term therapy in the treatment of nonproliferative DR.