The Early Treatment Diabetic Retinopathy Study (ETDRS) identified important risk factors for progression to high risk proliferative diabetic retinopathy (PDR) including retinopathy severity, decreased visual acuity, and high levels of hemoglobin A1C (HbA1c). Additional risk factors for progression to PDR are decreased hematocrit and increased serum lipids. The long-term benefit of improving glycemic control was evaluated by three large studies: the Diabetes Control and Complications Trial (DCCT), the Stockholm Interventional Study, and the UK prospective study. Several small studies, notably the Kuwamoto study, also evaluated the relationship between the glycemic control and diabetic retinopathy. Intensive glycemic control reduces the risk of any retinopathy by approximately 27%. Intensive therapy is most effective when initiated early in the course of the diabetes, demonstrating a beneficial effect over the course and progression of retinopathy. The long term benefits of the intensive glycemic control greatly outweigh the risk of "early worsening." Lowering elevated serum lipid levels has been shown to decrease the risk of cardiovascular morbidity. The ETDRS data suggest that lipid lowering may also decrease the risk of hard exudate formation and associated vision loss in patients with diabetic retinopathy. Preservation of vision may be an additional motivating factor for lowering serum lipid levels in persons with diabetic retinopathy and elevated serum lipid levels.