Detection of Retinal Neurovascular Coupling During Light Adaptation Using Optical Coherence Tomography Angiography: A...

Background: Neurovascular coupling (NVC) is a fundamental mechanism that dynamically matches retinal blood flow to neuronal metabolic demand. While dynamic vessel analysis (DVA) has been established for assessing NVC through flicker-light stimulation, the potential of optical coherence tomography angiography (OCTA) to detect NVC during physiological stimuli, such as dark-to-light adaptation, remains unexplored. Methods: In this prospective cross-sectional study, OCTA imaging was performed in both eyes of 22 healthy participants under dark-adapted (scotopic) and light-adapted (photopic) conditions. Each condition was measured three times consecutively. Macular and peripapillary vessel density (VD) were quantified. Results: After adjustment for measurement order and scan quality, light adaptation significantly increased peripapillary small VD (Δ = +1.30%, p = 0.046; 95% CI: 0.03-2.56%). Peripapillary all VD demonstrated a similar trend but remained borderline significant (Δ = +1.19%, p = 0.069). In contrast, macular VD showed no significant association with light adaptation (Δ = -0.91%, p = 0.11; 95% CI: -2.02 to 0.21%), but was significantly affected by scan quality (Δ = 1.62%, p < 0.001, 95% CI: 1.23-2.02%). Conclusions: In healthy older adults, OCTA detected an increase in peripapillary VD associated with dark-to-light adaptation, reflecting retinal vascular reactivity consistent with neurovascular coupling. The pronounced influence of scan quality and measurement order underscores their importance as critical confounding factors that must be carefully controlled in functional and longitudinal OCTA studies. Together, these findings highlight OCTA's promise as a non-invasive tool for assessing retinal neurovascular reactivity, while emphasizing the need for scan quality standardization and order correction to ensure reliable interpretation.