This paper describes the importance of diabetic retinopathy in the loss of visual function. We exposed the most important risk factors, such as diabetes duration, poor metabolic control, pregnancy, puberty, hypertension, poor control of blood lipids, renal disease, and sleep apnea syndrome. We describe the pathogenesis of the disease, small retinal vessel microangiopathies which produce extravasation, edema and ischemia phenomena. We put special emphasis on the vascular endothelial growth factor (VEGF) and its pathogenic importance. They are also described the main clinical symptoms as microaneurysms, intraretinal hemorrhages, hard and soft exudates, intraretinal microvascular abnormalities (IRMA), venous disorders, formation of new vessels and diabetic macular edema (the latter being the most common cause of vision loss). Finally we describe the latest diagnostic techniques and eye treatment, with special emphasis on obesity surgery importance as more important preventive factor to eliminate the predisposing and precipitating disease symptoms.