Impact of blood pressure on diabetic retinopathy

Although an elevated blood pressure has been proposed as one of the major risk factors for the development and acceleration of diabetic retinopathy, demonstration of an unequivocal association between high blood pressure and retinopathy is lacking. Recent epidemiologic, cross-sectional studies indicated a close relationship between elevated systolic blood pressure and diabetic retinopathy, particularly in NIDDM subjects. In IDDM patients, the association with diastolic blood pressure was more pronounced. In the few prospective studies with sufficient number of individuals and acceptable documentation of retinal changes, in addition to poor metabolic control elevated blood pressure emerged as one of the best predictors of the development of severe deterioration of diabetic eye disease. In the Joslin study the risk of progression to severe forms of diabetic retinopathy increased exponentially with hemoglobin A1c and was dramatically different in patients with diastolic blood pressure below versus above 70 mmHg. It was hypothesized that a very low diastolic blood pressure is associated with some mechanisms which are protective against progression of eye lesions. Treatment and adequate control of hypertension is strongly recommended in all diabetic patients, the optimal level of blood pressure reduction, however, is yet to be determined.