Impact of Aging and Light Stimulation Parameters on Retinal Hyperemia Responses in Functional Optical Coherence Tomography Angiography.

Purpose: The purpose of this study was to investigate the effect of physiological aging and flickering light stimulation (FLS) parameters on retinal functional hyperemia response using functional optical coherence tomography angiography (fOCTA). Methods: Healthy C57BL/6J mice were dark-adapted and anesthetized with pentobarbital, then fOCTA was used to measure retinal neurovascular coupling (rNVC) function. In the experiments of this paper, FLS protocols-including light color, intensity, flicker frequency, and duration-were set up to investigate the effects of FLS parameters on functional hyperemia response measurements in C57BL/6J mice (12 weeks). Then, we selected five groups (8, 12, 24, 32, and 48 weeks) of healthy mice at different ages for cross-sectional study to evaluate age-dependent rNVC changes. Results: The results of the parameter study show that both white and green FLS induce a significant retinal microvascular functional hyperemia response in healthy adult mice. Additionally, notable retinal functional hyperemia response is observed within the FLS intensity range exceeding 260 lux and the frequency range of 4 to 24 hertz (Hz). As the duration of FLS increases, the dynamic functional hyperemia response in retinal trilaminar vascular network becomes more pronounced. In the physiological aging model, the peak amplitude of rNVC at 12 to 24 weeks of age and significantly declines by 48 weeks. Conclusions: FLS parameters' optimization can enable low-dose, high-efficacy stimulation for precise rNVC evaluation in physiological and pathological contexts. In addition, the aging results reveal changes in neurovascular coupling function associated with physiological age. This study underscores the reliability of fOCTA as a noninvasive tool for evaluating retinal microvascular rNVC.