Diabetic retinopathy is a microvascular complication of diabetes and has complex and multifactorial pathogenesis. Cascade of biochemical changes characteristic to other diabetes vascular complications leads to structural changes of retinal capillaries some of which are unique. As a result of all processes at different pathogenesis levels there is an increase of free radicals concentration and decrease of antioxidant protection thus provoking an oxidative stress in retina and endothelial dysfunction with subsequent hypoxia and activation of growth factors and promotion of neovascularization leading to loss of vision in patients with type II diabetes mellitus. Consideration of oxidative stress reduction and restoration of retinal antioxidant system using exogenous antioxidants is a promising issue for further research.