Effect of nasal and temporal scanning tilt on whole and local macular vessel density measurement using OCTA

Purpose: To evaluate the effects of scanning tilt on the macular vessel density (VD) measurements in healthy subjects using optical coherence tomography angiography (OCTA). Methods: OCTA imaging was performed on healthy subjects to acquire nasal and temporal oblique scans. Quantitative analyses included as follows: (1) VD in whole-image, annular, and quadrant regions of the superficial capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillaris (CC) layer; (2) Foveal avascular zone (FAZ) parameters (area, perimeter, circularity index) in the SCP. Results: Twenty-eight eyes of 28 healthy participants were included. Nasal inclination significantly affected VD measurement in the SCP temporal quadrant, DCP nasal/temporal/inferior quadrants, and all CC regions (all P < 0.05). Temporal tilt influenced VD measurements in all regions except the SCP superior and temporal quadrants (all P < 0.05). While FAZ area and perimeter remained unaffected by tilt, temporal tilt significantly reduced FAZ circularity ( P = 0.022). Conclusion: The tilt of the OCTA scan has different effects on the VD measurements of the whole, annular, and quadrant regions of macular layers and the FAZ circularity index.