Abstract
Purpose :
To quantify retinal capillary reactivity to dark adaptation in healthy individuals.
Methods :
A custom-built functional optical coherence tomography angiography system (FOCTA, 200 kHz, axial resolution 4.2 μm, transverse resolution 10 μm) was used to image the 3x3mm perifoveal region in healthy adults. A flickering light stimulus in the optical path allowed simultaneous imaging and retinal stimulation under sequential photopic and scotopic conditions (40 minutes dark adaptation). Twenty volumetric scans were collected for each condition in a single imaging session. The following OCTA metrics were assessed: vessel diameter (VD), vessel skeleton density (VSD), flux, choriocapillaris flow deficit density (cFDD), and mean choriocapillaris flow deficit size (cMFDS). Analyses were performed for large (arteriole and venule) and small caliber (capillaries) vessels in the superficial (SRL) and deep retinal layers (DRL) as well as choriocapillaris (CC). Statistical significance was determined using paired and unpaired Student’s T-tests (p=0.05).
Results :
Three subjects (mean age 29±4 yrs) were included. The following results were obtained with dark adaptation: Large caliber VD increased from 21.63±2.1 to 23.81±1.6 μm, superficial VSD decreased from 0.202±0.01 to 0.197±0.01, deep VSD decreased from 0.05±0.01 to 0.04±0.01, superficial flux increased from 0.530±0.02 to 0.536±0.02, and deep flux increased from 0.47±0.04 to 0.50±0.04. The mean percentage difference between photopic and scotopic conditions for large caliber VD was most robust at +10.10% (P<0.001). Similar differences for VSD and flux for superficial and deep plexus were: -2.77% (p<0.001), +1.12% (p=0.04), -17.4% (p<0.001) and +5.03% (P<0.001) respectively. In the CC, there was an increase in flow deficit density under scotopic conditions (15.06%, P<0.001).
Conclusions :
Large caliber retinal vessels dilate under scotopic conditions. Capillary levels changes under scotopic conditions may suggest decreased flow. These findings suggest increased metabolic activity during dark adaptation.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.