Abstract
Purpose :
Maintaining sufficient blood flow in the retina is essential in sustaining neuronal health in ageing. Whilst optical coherence tomography angiography (OCTA) allows assessment of vascular perfusion, there are a lack of clinical tests that can be easily implemented to assess the retinal vascular response to stress. Here we describe a novel, non-invasive stress test to probe vascular regulation in the retina in young and older people.
Methods :
A custom-built device was used to deliver a flicker stimulus during simultaneous OCTA image acquisition (Spectralis, Heidelberg Engineering). Participants (n = 15 young, 23±1.4 years (mean±SD); n = 8 older, 75±7.1 years) were asked to abstain from caffeine, alcohol, and strenuous exercise 12 hours prior to imaging. Imaging was performed in the morning to control for diurnal fluctuation and pupils were dilated with tropicamide 0.5% (Mydriacyl). Images were obtained across each retinal layer were extracted and analysed for differences between baseline and flicker (relative change, %) using ImageJ. To examine changes to capillaries only, larger arteries and veins were masked in a secondary analysis. Mixed effects analysis was used to identify changes between baseline and age.
Results :
Flicker stimuli induced significant redistribution of blood across vascular layers compared to baseline in young eyes (p < 0.0001), with significant vasodilation in the nerve fibre layer vascular plexus (12.2±15.9%). The choroid (-16.7±16.7%) and choriocapillaris (-23.7±23.5%) did the opposite, demonstrating marked vasoconstriction, suggesting that choroidal blood flow is also modulated in response to increased metabolic demand in the inner retina from flicker stimulation. Greater choroidal vasoconstriction was moderately associated with overlying retinal fibre layer thickness (r2 = 0.43). This effect was less apparent in older adults, with subdued changes across vascular layers with flicker (p = 0.22) compared to baseline, but showing a significant effect between vascular layers x age (F(3.231, 26.49) = 3.4, p = 0.03).
Conclusions :
Functional tomography angiography is a novel clinical, non-invasive stress test to easily probe vascular regulation in the retina and allows for quantification of blood redistribution across the retina during flicker stimulation.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.