Abstract
Purpose :
An increase in neural activity in the retina results in a higher metabolic demand. To satisfy this need for oxygen and nutrients, retinal blood vessels dilate, this process is called neurovascular coupling. Here, we use a high spatial and temporal resolution modality: the Adaptive Optics Confocal Rolling Slit Ophthalmoscope (AO-CRSO) to measure flicker induced vasodilation.
Methods :
The retina of six healthy subjects was imaged using the AO-CRSO. A line scanning ophthalmoscope with which the confocal detection is done using the rolling shutter of a camera. By offsetting illumination and detection, this modality enables split detection imaging on a large field (2.5°x 4°) and at a high cadence (100 fps). For each subject, a 40 sec continuous acquisition on a 60-90 µm arteries was first taken without stimulation. Then, an acquisition with a 12.5 Hz green flicker stimulation was recorded (10 sec no flicker, 20 sec flicker, 20 sec no flicker). Using a peak detection algorithm, the vessel walls positions were measured at a 0.5 µm accuracy every 0.1 sec.
Results :
We observed a significant difference between the evolution profile of the artery diameter without stimulation (figure 2, a) and with stimulation (figure 2, b). We measured an artery maximum dilation of 5.2%±0.4% (standard error of the mean) during the flicker stimulation whereas the maximum dilation without flicker stimulation was of 2%±0.2%. Our approach allows us to isolate three factors that contribute to the variation in an artery's diameter : the cardiac cycle, which is responsible for the 1 Hz oscillation of the artery's diameter; vasomotion, an oscillation of the vessel walls at around 0.1 Hz and independent of the cardiac cycle; and neurovascular coupling, which causes the diameter to increase in response to light stimulation.
Conclusions :
We demonstrated a method to evaluate human neuro-vascular coupling in human retinas with a high spatial and temporal resolution and used it to measure flicker induced vasodilation on all subjects. Our approach enables us to observe the impact of the cardiac cycle, vasomotion and neuro-vascular coupling on the diameter of a retinal artery.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.