Abstract
Purpose :
Neurovascular coupling (NVC) modulates blood flow to match changing metabolic demand during neuronal excitation. Impairment of NVC leads to local tissue hypoxia and is associated in several retinal and neurological conditions. Given that outer retinal hypoxia is implicated in the pathology of age-related macular degeneration (AMD), we investigated neurovascular function of all major retinal vessels to determine whether NVC is impaired in eyes with AMD.
Methods :
Subjects with AMD and controls, aged ≥50 years and best-corrected visual acuity of 20/40 or better were recruited for the study. The vasculature of the superficial plexus, deep plexus, choriocapillaris and the choroid within the central 6x6 mm area of the retina was captured using a ZEISS Plex Elite optical coherence tomography angiography (OCTA). Flickering LED lights (10 Hz, 100 cd/m2) were used to induce an increase in retinal activity and metabolic demand, and thus an overall dilation of retinal vessels. In each eye, OCTA scans were acquired first without (conventional OCTA) and then with flicker lights. For each OCTA scan, the pixel area encompassed by blood vessels was calculated for each vascular layer. The percentage change in vessel area induced by flicker light was determined and compared between control and AMD eyes.
Results :
Fifteen subjects (20 eyes) with AMD and 7 controls (10 eyes) participated in the study. The mean age of the participants was 74.2 years for AMD and 68.5 years for controls. In control eyes, flicker light induced an overall increase in vessel area (vasodilation) in the superficial plexus (27.8%, p <0.001), deep plexus (8.8% at p <0.001) and the choriocapillaris (4.7%, p <0.001), but not in the choroid (0.05%, p = 0.957). Flicker-induced vasodilation was also observed in AMD eyes, however, to a lesser extent compared to control eyes. The average flicker-induced vasodilation in AMD eyes was 3.3% in the superficial plexus (p <0.001), 1.8% in deep plexus (p = 0.001), 0.2% in choriocapillaris (p = 0.756) and 1.1% in the choroid (p = 0.051).
Conclusions :
Neurovascular coupling-derived redistribution of blood flow through retinal layers can be assessed using OCTA coupled to flickering LED lights. The data from this study suggest that NVC is impaired across multiple layers in eyes with AMD, supporting the hypothesis that dysregulation of blood supply plays a role in AMD.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.