Macular retinal capillary hemodynamics in diabetic patients.

Macular retinal capillary hemodynamics was evaluated in 39 nonhypertensive insulin-dependent diabetic patients and 24 age-matched control subjects using the blue field entopic simulation technique. A statistically significant 25% increase in macular capillary flow velocity was observed among the diabetic eyes along with a 37% decrease in the density of the entoptically perceived leukocytes. When the eyes of diabetic patients were graded according to the modified composite scale of Klein et al, capillary flow velocity was elevated in the group without retinopathy as well as in those with mild background retinopathy and those with preproliferative or proliferative retinopathy. The density of the entopically perceived leukocytes was more severely reduced in those with retinopathy than in those without retinopathy but was poorly correlated with the composite grading scale. These results are consistent with the concept that in diabetes, capillary obstruction, either transient or permanent, may focally occur within the retina associated with vasodilation in the adjacent microvasculature because of relative tissue hypoxia.