The Role of Oxidative Stress after Retinal Laser Photocoagulation in Nonproliferative Diabetic Retinopathy

Diabetic retinopathy (DR) represents the most common chronic complication of diabetes, and it is the leading cause of new cases of blindness in patients between 20–74 years old in developed countries. Laser photocoagulation (LF) represents an efficacious approach to the treatment of DR. Oxidative factors, such as free radicals (FR), are continuously generated in aerobic organisms as a result of different metabolic processes. It is well known that oxidative stress plays a role in the development of DR. The aim of this study was to evaluate the thermal effects of the scatter retinal laser photocoagulation technique on the production of FR. A total of 90 patients were enrolled in this study. They were divided in 3 groups: 30 diabetic patients with DR, 30 diabetic patients without DR, and 30 control individuals without diabetes mellitus (DM). Full scatter retinal LF was performed in all patients with DR. We measured the concentrations of superoxide dismutase (SOD), glutathione peroxidase (GPOD), catalase, and total antioxidative status (TAS). Of the 30 DR patients, 13 showed the appearance or worsening of macular edema after LF, whereas the other 17 patients showed no change. Thirty days after LF, improvement in visual acuity was observed, but this change was not statistically significant. The mean plasma or erythrocyte lysate concentrations of various antioxidants were significantly lower in the diabetic patients without DR compared to the individuals without DM and in the diabetic patients with DR compared to the individuals without DM; the diabetic patients with DR did not show lower concentrations of the antioxidants compared to the diabetic patients without DR. The concentrations of SOD, GPOD, catalase, and TAS were significantly lower in the diabetic patients with DR after retinal scatter LF, which could be the consequence of retinal oxidative stress caused by the LF thermal effect