Abstract
Purpose :
To investigate the impact of scan tilt on quantitative assessments using swept-source optical coherence tomography angiography (SS-OCTA) in healthy subjects.
Methods :
Healthy subjects were imaged with a SS-OCTA system (PLEX Elite 9000, Carl Zeiss Meditec Inc, Dublin, California, USA) using a 6 x 6 mm scan pattern. After a standard scan was obtained through the center of the pupil, tilted scans were obtained by moving the OCT beam entrance position horizontally. The tilting angle was measured from the B-scan image and the flattest (horizontal) and the most tilted images were selected for comparative analysis. En face images of superficial retinal plexus (SCP), deep retinal capillary plexus (DCP) and choriocapillaris (CC) layers were obtained. FAZ area, vessel density (VD) and vessel length density (VLD) from the SCP and DCP, and CC flow deficits (FD) were computed and compared between horizontal and tilted images.
Results :
Twenty-seven normal eyes of 17 subjects with a mean age of 39.3±5.9 years were included in this analysis. The FAZ area, VD and VLD of both the SCP and DCP were not significantly different between horizontal and tilted images. The CC FD, however, was significantly higher in horizontal images compared with tilted images (21.65±2.41 % vs 21.06±2.19 %, P=0.005).
Conclusions :
CC FD measurements may be significantly affected by the position of the scanning beam and resultant scan tilting. These findings may need to be considered when analyzing tilted en face OCTA images, which are commonly observed in myopic eyes with steeper posterior curvatures and in wider field OCTA scans.
This is a 2020 ARVO Annual Meeting abstract.