Abstract
Purpose :
Evaluate the relative blood flow velocity in superficial and deep retinal capillary network using high-speed SS-OCTA and variable interscan time analysis (VISTA).
Methods :
OCTA imaging of 8 normal eyes from 4 subjects was performed using a prototype 400 kHz SS-OCT system (Topcon Corp, Tokyo, Japan). The circle scan with a diameter of 1.4 mm was moved spirally from macula toward the φ6 mm area. The advantage of the use of circle scan instead of the conventional raster scan was the elimination of the scanner’s flyback motion and shortens the interscan time. After applying a three-dimensional motion correction algorithm, flow parameters were calculated from OCTA signal intensity by the VISTA method. En-face OCTA image was extracted with a 3×3 mm2 area centered on the macula. The relative blood flow velocities in the superficial and deep layers of the retinal capillary plexus were evaluated where the vessels larger than 30 μm in diameter were excluded from the evaluation in this study.
Results :
The proposed method successfully produced VISTA images over the entire imaging area without notable motion artifacts. The relative blood flow velocity within 3×3 mm2 region centered on the macula was 1.41±0.11 ms-1 in the superficial and 0.77±0.12 ms-1 in the deep layer. Capillary blood flow in the superficial retina was significantly faster than that in the deep retina (P < 0.01).
Conclusions :
The combination of the high-speed SS-OCTA and VISTA method enabled to measure the relative blood flow velocity in the retinal capillary network. The novel scan protocol and motion correction algorithm improved the reliability of the measurement even though the relatively lengthy data acquisition time which is inherent to VISTA imaging. Proposed new scan method has a capability to expand the scan area to peripheral region with preserving appropriate interscan time.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.