Effect of flicker on macular blood flow assessed by the blue field simulation technique.

PURPOSE To determine the effect of diffuse luminance flicker on the motion of leukocytes in the retinal macular capillaries of normal subjects. METHODS Using the blue field simulation technique, subjects were asked to match the motion of simulated leukocytes displayed on a video monitor to that of their own entoptically seen white blood cells (WBCs). The changes in velocity and density of the WBCs were recorded after stimulation with diffuse luminance flicker of various durations (0 to 16 seconds), either immediately or at various delays (2, 4, 8 seconds) after cessation of the stimulus. RESULTS White blood cell velocity increased as flicker duration increased from 0 to 16 seconds. After cessation of flicker, leukocyte motion decreased to baseline within 15 seconds. CONCLUSIONS The authors' findings suggest a coupling between retinal neural activity and blood flow in the macular region of the retina. The rapidity of both the flicker-induced increase in WBC motion and the disappearance of the effect after flicker cessation resembles the time course of blood flow changes previously observed in the microcirculation of the cat optic nerve.