Plexus-Specific Effect of Flicker-Light Stimulation on the Retinal Microvasculature Assessed with Optical Coherence Tomography Angiography.

In neural tissues, the coupling between neural activity and blood flow is a physiological key principle in blood flow regulation. We used optical coherence tomography angiography to investigate stimulus-evoked hemodynamic responses in different microvascular layers of the human retina. Twenty-two healthy subjects were included. Vessel density before and during light stimulation was measured using optical coherence tomography angiography and assessed for the superficial, intermediate and deep capillary plexus of the retinal circulation. Volumetric blood flow was measured using a custom-built Doppler optical coherence tomography system. Our results show that flicker stimulation induced a significant increase in the vessel density of +9.9±6.7% in the superficial capillary plexus, +6.6±1.7% in the intermediate capillary plexus and +4.9±2.3% in the deep capillary plexus. The hyperemic response of the superficial capillary plexus was significantly higher compared to the intermediate capillary plexus (p=0.02) and deep capillary plexus (p=0.002). Volumetric retinal blood flow increased by +39.9±34.9% in arteries and by +29.8±16.8% in veins. In conclusion, we showed a strong increase in the retinal microvascular density in response to light stimulation, with the most pronounced effect in the superficial capillary plexus. This is compatible with the hypothesis that the microvasculature exerts an important function in mediating functional hyperemia in humans.