Diurnal Variations of Peripapillary and Macular Vessel Density in Glaucomatous Eyes Using Ocular Coherence Tomography Angiography

PURPOSE:To investigate the diurnal variation in peripapillary and macular vessel density (VD) measurements using optical coherence tomography angiography (OCT-A) and its correlation to intraocular pressure (IOP) changes in glaucoma patients. METHODS:Prospective, observational cross-sectional study including 37 patients (74 eyes; age, 63.8±12.9▒y) with open angle glaucoma. OCT-A imaging and IOP measurements were performed at 08:00, 11:00, 14:00, and 16:00 on a single day. At each time-point, two scan protocols were used to generate 3-dimensional en-face OCT angiograms4.5×4.5-mm scan centered on optic nerve head and 6×6-mm scan centered on the fovea. For each scan mode, the “Radial Peripapillary Capillary (RPC)” segment, composed of the vasculature of the RNFL and ganglion cell layer, was calculated. Two trained readers reviewed OCT-A image quality. Only scans with signal strength intensity (SSI) higher than 46 and without image artifacts interfering with measurements were included. Variation in VD measurements assessed using analysis of variance (ANOVA) and the association between VD and IOP changes assessed using linear mixed modeling methods. RESULTS:The ONH and peripapillary VD measurements at 14:00 and 16:00 time points were greater than the measurements at 08:00 and 11:00 time points. The 14:00 and 16:00 VD measurements were statistically significantly greater (P