Retinal complications of diabetes mellitus are chronic but late functional signs can lead to delayed diagnosis and treatments. Light coagulation (argon laser radiation) is recognized for its efficiency at the stage of "mature" retinopathy, converting the prognosis of a disease which was leading to blindness. Photocoagulation is not used in the early stages (early or strictly posterior pole diabetic retinopathy); partial regression or stabilization can be hoped with intensive medical treatment of diabetes. Treatment of diabetes could become the best preventive treatment. Light coagulation is used at stages when the disease is not reversible (non or preproliferative and proliferative). In tractional retinal detachment surgery remains active, always corresponding to too late treatments. Although pharmacology has progressed (inhibitors of platelet agregation and of non enzymatic glycation) medical therapy remains controversial.