A Systematic Review

DIABETES MELLITUS AFFECTS 200 million people worldwide, including 20 million in the United States alone. Diabetic retinopathy (DR), a specific microvascular complication of diabetes, is the leading cause of blindness in working-aged persons in the United States. The prevalence of DR increases with duration of diabetes, and nearly all persons with type 1 diabetes and more than 60% of those with type 2 have some retinopathy after 20 years. The major risk factors for DR have been reported from epidemiologic studies and are summarized in the BOX. Diabetic retinopathy can be classified into 2 stages: nonproliferative and proliferative. The earliest visible signs in nonproliferative DR are microaneurysms and retinal hemorrhages (FIGURE, A). Progressive capillary nonperfusion is accompanied by development of cotton-wool spots, venous beading, and intraretinal microvascular abnormalities. Proliferative DR occurs with further retinal ischemia and is characterized by the growth of new blood vessels on the surface of the retina or the optic disc (Figure, B). These abnormal vessels may bleed, resulting in vitreous hemorrhage, subsequent fibrosis, and tractional retinal detachment. Diabetic macular edema (DME), which can occur at any stage of DR, is characterized by increased vascular permeability and the deposition of hard exudates at the central retina (Figure, A). Diabetic macular edema is now the principal cause of vision loss in persons with diabetes. Primary interventions, such as intensive glycemic and blood pressure control, can reduce the incidence of DR, while secondary interventions, such as laser photocoagulation, may See also Patient Page.