Retinal blood flow in healthy young subjects.

PURPOSE To characterize total retinal blood flow in a group of healthy subjects. METHODS Included in this study were 64 healthy volunteers. Retinal venous diameters were measured using a dynamic vessel analyzer. Retinal blood velocities were measured using bidirectional laser Doppler velocimetry. All vessels with a diameter of >60 μm entering the optic nerve head were measured. Total retinal blood flow was measured by summing up all data from the individually measured vessels. In a subgroup of 10 healthy subjects measurements were also taken from the arterioles, and results obtained for total retinal blood flow as measured both from retinal venules and from retinal arterioles were compared. RESULTS Total retinal blood flow was 44.0 ± 13.3 μL/min. Retinal blood flow was highest in the temporal inferior quadrant, followed by the temporal superior quadrant, the nasal inferior quadrant, and the nasal superior quadrant (P < 0.001 each). In all quadrants retinal blood velocities were linearly correlated to vessel diameters. Retinal blood flow as measured in retinal venules (42.1 ± 13.0 μL/min) and in retinal arterioles (43.3 ± 12.1 μL/min) was similar (P = 0.16). CONCLUSIONS The present study provides reference values for total retinal blood flow in 64 healthy subjects. The interindividual variability in retinal blood flow is high, making it unlikely that individual diagnostics can be based on measurements of retinal blood flow. Total retinal blood flow, however, may be important in risk stratification, which needs to be proven in future studies.