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Qinqin Zhang, Ruikang Wang; Capillary velocimetry measurement in human eyes based on commercial SSOCTA. Invest. Ophthalmol. Vis. Sci. 2021;62(11):51.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the capillary blood flow speed on human retina in vivo based on commercial OCTA device with modified scanning protocols (B-M mode)
A 1060 nm swept source OCTA engine (PLEX® Elite 9000 (ZEISS, Dublin, CA)) running at 200 kHz A-line rate with motion tracking mechanism was utilized in our study. New scanning protocol with 200 A-lines x 200 B-scans covering ~ 2mm x 2mm with 10 repetitions was designed and implemented on the device for velocimetry estimation. The time interval between the adjacent B scans is ~1ms with a distinguishable velocity range from 0 mm/s to ~0.5mm/s according to the theorical analysis . The blood flow speeds of capillary were statistically separated by using Eigen decomposition (ED) approach. Layers both from retina and choroid were segmented to investigate the speed variations in different plexus, including the superficial retinal layer (SRL), deep retinal layer (DRL), ORCC layer and choriocapillaris (CC) layers. Each speed that separated by the eigen values was filtered and displayed to demonstrate the speed variations of blood flow in each layer
Normal eyes and diseased eyes were enrolled in this study. The ED based velocimetry has shown the capability of differentiating the speed of blood flow (Figure 1) at capillary level. The larger eigen value containing larger portion of energy corresponds to lower speed and vice versa. In normal eyes, the blood flow speeds in retina and CC have a relatively uniform distribution across all the eigen values when compared with pathological eyes. In pathological eyes, abnormal blood flow speeds were observed. A faster speed associated with the trunk of the CNV lesion and slower speeds associated with the lesion extremities were observed in wet AMD eyes
The modified scanning protocol in the commercial device with a time interval of ~ 1ms has the capability to differentiate the blood flow speed of capillary in human eye based on the ED approach. The faster A-line rate (200 kHz) of the swept source engine enabled a large field of view (up to 2 x 2mm) that is helpful for the investigations of the ocular pathologies. The results showed the velocimetry may play a role not only in the investigations of ocular disease but also in developing endpoints for therapeutic clinical trials
This is a 2021 Imaging in the Eye Conference abstract.
Figure 1 an example of the blood flow speed variation in retinal and choriocapillaris layers in a normal eye
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