Investigating neurovascular responses of the peripapillary retinal artery to focal flicker stimulation of temporal retinal neurons in the living human eye using AO-OCT.

We have developed an AO-OCT-based method to characterize microscopic vasodilatory responses of peripapillary major retinal artery (ppRA) to the focal luminous flicker stimulation of peripheral retinal neurons (>15° temporal to the fovea) with various mean illuminance levels, frequencies, and spatial patterns in the living human eye. The results have demonstrated that our proposed method can effectively measure transient, microscopic vasodilatory responses of the ppRA to the focal flicker stimulation, which increased monotonically with mean illuminance levels (1, 5 and 11lx), and exhibited frequency band-pass-like behavior (2, 5, 10, 15, 20 and 30 Hz) consistent with expected increases in the activities of retinal ganglion cells (RGCs) and their associated axons. We also found that the proposed method can be used to measure the spatial interdependency of their neurovascular responses: superior arcuate ppRA response to the superior-temporal flicker was 58% greater than that to the inferior-temporal flicker, and the inferior arcuate ppRA response to the inferior-temporal flicker was 86% greater than that to the superior-temporal flicker. Collectively, these results indicate that, using the proposed method, we can now test the hypothesis that major retinal arteries respond in an orchestrated manner to increased firing activities of RGCs and their associated axons, by accounting for the spatial coordinates between the stimulated neurons and the ppRA arcs in the living human eye.