Abstract
Purpose :
To measure the reactive change in neurovascular activity at the cellular scale in response to well-controlled flicker light stimulation in the living human eye using a multifunctional adaptive optics optical coherence tomography (AO-OCT).
Methods :
The peripapillary RNFL (pRNFL) regions with 3.5mm around the ONH were selected to acquire multiple videos for each eye of two well-trained, healthy subjects (A and B) using multifunctional AO-OCT (Fig.1). We used an external LED array (white light), which flickered at 5 Hz and brightness of 2 or 20 lx with 100% modulation depth, to illuminate the temporal portion of the retina (> 8° temporal to the fovea) where only the downstream cells were exposed to the stimulus. After pupil dilation, we collected two datasets with and without flicker light stimulation by scanning a beam over 1°X 1° FOV with A-line spatial sampling of 256 x 256. Each dataset comprised 15 repeated scans of 4-second volume video (16 consecutive volume images). After registering and averaging hundreds of AO-OCT volume images, we computed the reflectance at the top and bottom surface of major and intermediate-size vessels, vessel depth diameters, and angiogram at the pRNFL tissue that includes peripapillary radial capillaries.
Results :
The major vein around the ONH (baseline diameter= 98.6 µm) showed a significant increase in diameter by 5.3%, while an intermediate vessel (baseline diameter= 13.5 µm) increased by 14.1% with the 20-lx flicker light stimulation in subject A (Fig.2). The vessel diameters increased with 2-lx flicker light stimulation by 5% in subject A’s artery, 1.2% in subject B’s artery, and 2.2% in subject B’s vein. The AO-OCT reflectance was significantly changed (increase or decrease), indicating the change in tissue directionality (or deformation) related to the vasodilation. The AO-OCT angiogram in the pRNFL tissue increased significantly by 1 to 2% with 2-lx and by 3% with 20-lx flicker light stimulations. These results indicate the effect of local flicker stimulation on the upstream vasodilation by stimulating downstream cells. Moreover, flicker stimulation could have induced dynamics within pRNFL tissue by stimulating the downstream retinal ganglion cells.
Conclusions :
We have demonstrated in vivo measurements of neurovascular reactivity at pRNFL in response to weak and local flicker light stimulation using multifunctional AO-OCT.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.