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AbstractDO.01.09 Measurement of retinal blood flow during euglycemic euinsulinemic clamps in patients with diabetes Schmetterer L.1,2, Polska E.1, Garhöfer G.1
1Universitätsklinik für Klinische Pharmakologie, 2Zentrum für Biomedizinische Technik und Physik, Medizinische Universität Wien Objective: In the recent years numerous studies on retinal blood flow in diabetic retinopathy have been published, but the results are contradictory. This may be related to methodological aspects, patient selection and glycemic control. The latter point is critical, because both insulin and glucose induce ocular vasodilatation. Hence, we studied retinal blood flow in diabetic patients during euglycemic euinsulinemic clamps.
Methods: In this study 16 patients with insulin dependent diabetes and no or mild non-proliferative diabetic retinopathy were included. 16 healthy age- and sex-matched subjects served as controls. In diabetic patients retinal blood flow was measured in the morning before the insulin morning dose and during euglycemic euinsulinemic clamps. Retinal blood flow was measured by combining retinal venous diameter data retinal blood velocity data. To gain information on total retinal blood flow all veins entering the optic nerve were measured and the data of the individual vessels were added.
Results: Before morning insulin dose plasma glucose was 176 ± 21 mg/dl. This plasma glucose level was reduced to 102 ± 4 mg/dl during the euinsulinemic clamp. Retinal blood flow was 51.4 ± 5.5 µl/min before the clamp. During the euglycemic euinsulinemic clamp retinal blood flow was significantly reduced to 42.1 ± 5.2 µl/min (p < 0.01). As compared to retinal blood flow in the healthy control group (41.2 ± 4.1 µl/min) retinal blood flow in diabetic patients was increased before the euglycemic euinsulinemic clamps (p < 0.05), but not when blood glucose was normalized (p > 0.6).
Conclusions: The present study indicates that retinal blood flow is increased in patients with diabetes at high plasma glucose levels, but not during euglycemic euinsulinemic clamps. This indicates that retinal blood flow is characterized by significant fluctuations when glucose plasma levels fluctuate.
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