Diurnal Variation in Choroidal Parameters Among Healthy Subjects Using Wide-Field Swept-Source Optical Coherence Tomography Angiography

Purpose: The purpose of this study was to evaluate the diurnal variation in choroidal parameters in a wide field area among healthy subjects and to identify correlations between choroidal luminal area and stromal area and various systemic factors. Methods: In this cross-sectional study, 42 eyes from 21 healthy participants (mean age = 32.4 +/- 8.8 years) were examined using wide -field swept -source optical coherence tomography angiography (WF SS-OCTA, 24 mm x 20 mm). Measurements of choroidal parameters, including choroidal volume (CV), choroidal thickness (CT), choroidal vessel volume (CVV), and choroidal stromal volume (CSV), were taken at 8:00, 12:00, 18:00, and 22:00. Systemic factors, such as blood pressure and heart rate, were concurrently monitored. Results: Our study observed significant diurnal variations in the mean total CV, CT, CVV, and CSV, with minimum measurements around 12:00 ( P < 0.001) and peak values at 22:00 ( P < 0.001). Furthermore, changes in CV in specific regions were more closely associated with fluctuations in CVV than CSV in the same regions. No significant diurnal variations were found in systolic ( P = 0.137) or diastolic blood pressure ( P = 0.236), whereas significant variations were observed in the heart rate ( P = 0.001). Conclusions: Our study reveals diurnal variations in choroidal parameters and their associations, emphasizing that changes in choroidal volume relate more to the luminal than the stromal area in vessel -rich regions. This enhances our understanding of choroidal-related ocular diseases. Translational Relevance: Regions with higher choroidal vasculature observed greater choroidal volume changes.