Current approaches and perspectives in the medical treatment of diabetic retinopathy.

Diabetic retinopathy is a leading cause of visual loss in industrialized countries. Its classification includes preclinical, nonproliferative (mild, moderate, and severe or preproliferative diabetic retinopathy) and proliferative stages (low risk, high risk, and advanced). Diabetic maculopathy (exudative, edematous, or ischemic) may be associated with either nonproliferative or proliferative retinopathy. Prevention requires the tightest possible control of both blood glucose and blood pressure. Laser photocoagulation remains the only procedure recommended for severe nonproliferative or proliferative retinopathy and maculopathy. Since it reduces legal blindness by more than 90% in proliferative retinopathy and prevents severe sight loss in diabetic maculopathy, photocoagulation is probably one of the most effective forms of treatment known today. Less destructive approaches are desirable, however, and those currently under phase 3 trial include blockade of angiotensin receptors, the beta-isoform of protein kinase C, and growth hormone secretion by long-acting analogues of somatostatin. Evidence from past randomized controlled studies does not support a role for inhibitors of platelet aggregation, aldose reductase, and advanced glycosylation end products in the prevention/treatment of retinopathy. Future approaches might include the use of thiamine and its analogues in the primary and secondary prevention of early retinopathy and blockers of vascular endothelial growth factor/vascular permeability factor in more advanced stages.