Objective: Changes in the microcirculation per se may precede macrovascular changes, hence, may present a good surrogate for monitoring vascular changes during treatment. Using retinal vascular imaging techniques, we attempted to investigate the microvasular benefit of a single LDL apheresis in hypercholesterolemia. Methods: Twenty-one hypercholesterolemic patients (57±15 years) on regular LDL apheresis treatment, seven women and 14 men, were examined for retinal endothelial function before and after a single LDL apheresis. The Dynamic Vessel Analyzer was applied for static and dynamic retinal vessel analysis. Retinal vessel diameter was measured at rest and during flicker light stimulation. Changes in vasodilation are expressed as percent changes over baseline. Results: Cholesterol fractions and triglycerides were reduced by 21-74 % by the LDL apheresis procedure. In hypercholesterolemic patients, flicker-induced vasodilation was diminished in both retinal arterioles and venules, but had significantly improved in retinal venules after a single LDL apheresis (p = 0.013). This increase in vasodilatory capacity of retinal venules was linked to a wider basal retinal venular caliber (p = 0.031), but was unrelated to changes in serum lipids (p > 0.05). Conclusion: In hypercholesterolemia, abnormal retinal autoregulation is improved by a single LDL apheresis. Our findings suggest that venules represent a dynamic component, which is highly responsive to metabolic changes in the microcirculation.