Abstract
Purpose :
Prior imaging studies in both animals and humans have reported conflicting results about the impact of dark adaptation on choroidal blood flow (CBF). Using laser speckle flowgraphy (LSFG), we aimed to understand the effects of dark adaptation and fixation lights on macular CBF.
Methods :
Healthy adult subjects (N=10) with no known vascular or ophthalmic diseases were recruited. Baseline CBF measures centered on the macula within 1.5 mm, 2.25 mm, and 3.0 mm diameter were collected using the NAVI-Lite LSFG device under ambient light conditions. Experiment 1 obtained serial CBF measures in the dark after 20 minutes of dark adaptation (without an internal fixation light). Next, Experiment 2 collected serial CBF measures after exposure to a 10-second and a 60-second exposure to a monochromatic internal fixation light (570 nm) while under dark adaptation. Percent change from baseline (ambient light on, fixation light off) for Experiment 1 and percent change from dark adaptation (ambient light off, fixation light off) for Experiment 2 were calculated for each subsequent CBF measures from each patient. These percent changes were used for statistical analyses by mixed effect models.
Results :
In Experiment 1, CBF demonstrated a gradual significant decline over the 20-minute dark adaptation (p<0.01) across all regions of interest. Compared to baseline, CBF was significantly decreased at both 15-minute (p<0.05) and 20-minute time points of dark adaptation (p<0.01). Analysis of specific vascular metrics (e.g. vascular resistance, heart rate) did not demonstrate significant changes across all time points. In Experiment 2, neither the 10-second nor the 60-second exposure to the internal fixation light significantly altered CBF under dark-adapted conditions.
Conclusions :
We demonstrate that LSFG measures of CBF steadily decrease during dark adaptation reaching its nadir at 20 minutes. Short and longer duration exposures to a 570-nm internal fixation do not significantly alter CBF during dark adaptation.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.