RETINAL BLOOD-FLOW CHANGES IN PATIENTS WITH INSULIN-DEPENDENT DIABETES-MELLITUS AND NO DIABETIC-RETINOPATHY - A VIDEO FLUORESCEIN ANGIOGRAPHY STUDY

Purpose. The authors investigated retinal blood flow changes in patien ts with insulin-dependent diabetes mellitus (IDDM) and no diabetic ret inopathy compared to age-matched subjects without diabetes. They also investigated whether blood glucose levels could modulate retinal blood flow in these patients with diabetes and whether this modulation woul d impact retinal blood flow data used in cross-sectional studies asses sing changes in retinal blood flow. Methods, Retinal blood flow was me asured using video fluorescein angiography, and blood glucose levels w ere manipulated using glucose clamp methodologies with continuous basa l insulin replacement. Blood glucose levels were clamped at 100, 200, and 300 mg/dl. Retinal blood flow measurements were performed at each blood glucose level after subjects had been stabilized for an hour at each of the different blood glucose levels. Results. Retinal blood flo w was found to be significantly decreased (P < 0.01) in the group of p atients with no diabetic retinopathy (19.4 +/- 4.6 arbitrary units [AU ]) compared to retinal blood flow in subjects without diabetes (28.7 /- 6.4 AU). During glucose clamp adjustment of blood glucose levels, i t was found that as blood glucose levels were increased from euglycemi a (100 mg/dl) to 200 mg/dl and to 300 mg/dl, retinal blood flow was si gnificantly increased at the 200 mg/dl level (21.5 +/- 4.7 AU, P < 0.0 5) and at the 300 md/dl level (25.9 +/- 8.8 AU, P < 0.01) compared to the 100 mg/dl level (16.3 +/- 3.8 AU). In addition, the retinal blood flow at the 100 and 200 mg/dl levels was significantly reduced (P < 0. 01) compared to nondiabetic retinal blood flow (28.7 +/- 6.4 AU). Conc lusions. Retinal blood flow was found to be decreased in patients with IDDM with no diabetic retinopathy, and acute elevations in blood gluc ose levels resulted in increased retinal blood flow in these patients. The acute modulation of retinal blood flow by blood glucose levels sh ould be considered in cross-sectional studies investigating retinal bl ood flow changes in patients with diabetes. The results from this stud y indicate that if blood glucose levels are not accounted for in the a nalyses, larger populations would have to be studied to demonstrate st atistically significant differences between groups with and without di abetes.