Diabetic retinopathy is a major cause of blindness in adults. Ever since the United Kingdom Prospective Diabetes Study (UKPDS) and Diabetes Control and Complications Trials (DCCT),1 2 3 intensive control of blood glucose and blood pressure has been the mainstay of the systemic management of diabetic retinopathy. Because epidemiological studies indicated a direct and continuous relation between the degree of hyperglycaemia and the risk of diabetic retinopathy,4 the control of blood sugar and blood pressure has been guided by the belief that “lower is better.”

Three new trials in the past year—Action in Diabetes and Vascular Disease (ADVANCE), the Diabetic Retinopathy Candesartan Trials (DIRECT), and Fenofibrate Intervention and Event Lowering in Diabetes (FIELD)—have provided new insights into the effectiveness and limitations of systemic treatment for diabetic retinopathy.

ADVANCE recruited 11 140 patients with type 2 diabetes and found that lowering glycated haemoglobin to 6.5% or less had no measurable effect on five year incident retinopathy (6.0% intensive treatment v 6.3% standard treatment).5 Systolic and diastolic blood pressures were also lowered by a mean of 5.6 mm Hg and 2.2 mm Hg, respectively, from a starting value of 145/81 mm Hg. However, this considerable reduction did not alter the four year incidence or progression of diabetic retinopathy …