Diurnal Variation in Ocular Morphology

All measurements were performed on each subject without prior pupil dilation at three consecutive sessions (9 AM, 3 PM and 9 PM) within one day. An interval of six hours had to be between each measurement. One eye of each subject was chosen randomly before the first acquisition. To avoid fluctuations in blood pressure and heart rate, the measurements were taken each time after a waiting period of ten minutes in a sitting position and the participants were prohibited to consume caffeine prior to each visit. Each session included a high-resolution three-layer en face OCT-A scan of macula region (including SVP, ICP and DCP) and a high-speed OCT scan with enhanced depth imaging mode (EDI) to determine subfoveal CT, both by Heidelberg Spectralis II OCT (Heidelberg Engineering, Heidelberg, Germany). In addition, AL was measured with IOL master 500 (Carl Zeiss Meditec AG, Jena, Germany). All OCT-A scans were recorded on a 2.9 x 2.9 mm² window with a 15° x 15° angle and a lateral resolution of 5.7 μm/pixel. Subfoveal CT was measured manually with a vertical distance between the hyperreflective line of Bruch’s membrane and the choroid-scleral interface.