RETINAL CIRCULATORY ABNORMALITIES IN TYPE-1 DIABETES

Purpose. To quantify retinal circulatory abnormalities in patients wit h type 1 diabetes; to compare blood speed and blood flow in major temp oral retinal arteries as well as total retinal arterial cross-section measured in patients to that measured in controls without diabetes; to determine which factors are related to the measured abnormalities wit hin the patient group. Methods. The laser Doppler technique and monoch romatic fundus photography were used to measure retinal circulatory pa rameters in 39 patients with type 1 diabetes with duration of diabetes between 7 and 20 years and 13 age-matched controls without diabetes. Blood pressure, intraocular pressure, and heart rate were measured in all subjects. Glycosylated hemoglobin was measured in the patients. Re tinopathy was assessed using standardized color fundus photography and fluorescein angiography. Results. Total retinal arterial cross-sectio n was, on average, 17% higher (P = 0.001) in the patients than in the controls, and it increased with increasing duration of diabetes (P = 0 .006). Arterial blood speed was, on average, 33% lower (P = 0.0001) in the patients than in the controls, and it decreased with increasing d uration of diabetes (P = 0.03). Conclusions. The retinal circulation o f patients with type 1 diabetes with no retinopathy or background reti nopathy is characterized by dilated major arteries with reduced blood speeds. Dilation of the larger retinal arteries, with the accompanying decrease in vascular resistance to flow in those vessels, appears to counteract an increase in resistance to flow at the level of the small er retinal vessels.