Retinal blood flow in patients with diabetes during normalized insulin and glucose plasma levels

Abstract

Abstract Purpose Ocular blood flow studies in patients with diabetes showed contradictory results. One of the reasons for these discrepancies is related to glycemic control, because glucose and insulin have been shown to induce ocular vasodilatation. Hence, we performed a study in diabetic patients measuring ocular blood flow during euglycemic euisoglycemic clamps. Methods 16 patients with insulin dependent diabetes, no or mild non‐proliferative diabetic retinopathy and serum cholesterol levels < 250 mg/dl and 16 healthy sex‐ and age‐matched controls were included in the study. Retinal blood flow was measured in diabetic patients before the insulin morning dose and during euglycemic euinsulinemic clamps. For the assessment of retinal blood flow the Retinal Vessel Analyzer and bi‐directional laser Doppler velocimetry were used. All veins entering the optic nerve head were measured to gain information on total retinal blood flow. Results Plasma glucose levels decreased from 176±21 mg/dl before morning insulin to 102±4 mg/dl during the euinsulinemic clamp. Retinal blood flow was reduced significantly from 51.4±5.5 µl/min before the clamp to 42.1±5.2µl/min during the euglycemic euinsulinemic clamps (p<0.01). As compared to the healthy control group retinal blood flow was increased before the clamps, but not during euglycemic euinsulinemic conditions. Conclusion The present study indicates that retinal blood flow is increased in diabetic patients during high blood glucose levels. Retinal blood flow values are, however, comparable to healthy controls during euglycemic euisoglycemic clamps.