Repeatability and diurnal variation of capillary vessel flow densitymeasurements in normal subjects using optical coherence tomography angiography

Aim: To evaluate the repeatability and diurnal variation of retinal vascular density and foveal avascular zone(FAZ) measurements via optical coherence tomography angiography. Material and Methods: Two measurements between 10 minutes in the morning hours and one measurement in the evening hours at the same day were done with RTVue XR Avanti OKT with AngioVue software on 41 healthy subjects. FAZ area, FAZ perimetry, foveal density (FD), whole image, foveal, parafoveal, perifoveal vessel density (VD) of superficial capillary plexus (SCP) and deep capillary plexus (DCP), foveal, parafoveal and perifoveal macular thickness (MT) parameters were evaluated with coefficient of repeatability (CR), Bland-Altman plots and intraclass correlation (ICC). Results: OCTA measurements showed very good repeatability for FAZ area, FAZ perimetry,FD, foveal VD of SCP and DCP, foveal, parafoveal and perifoveal MT parameters(ICC data are between 0,82 and 0,99.). CR of these parameters are %5.4, %4.3, %8.85, %19.19, %12.62, %1.44, %1.17 and %1.6 respectively. ICC for whole image VD of SCP and DCP are 0,72; 0,4 and CR values are %7.5, %15.98 respectively. The similar results were obtained for diurnal rhythm investigation. Conclusion: OCTA is a new technology with very good repeatability for FAZ, MT, foveal VD of SCP and DCP parameters. There is no diurnal rhythm for VD of retinal capillaries, FAZ parameters, MT parameters. Keywords: optical coherence tomography angiography, diurnal rhythm, repeatability, vessel density, macular thickness