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Qinqin Zhang, Ruikang K Wang; OCTA capillary velocimetry with high resolution on human eye. Invest. Ophthalmol. Vis. Sci. 2020;61(7):2724.
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© ARVO (1962-2015); The Authors (2016-present)
To develop capillary velocimetry methodology for quantifying retinal blood flow in vivo
A home-built swept source OCTA engine running at 200 kHz A-line rate with a central wavelength of 1060 nm was utilized in our study, where the incident beam size of ~3.5mm was achieved on the cornea, resulting in ~7.0 um lateral resolution on the retina. A B-mode scanning protocol with 220 A-lines x 220 B-scans covering ~ 2mm x 2mm with 10 repetitions was designed and implemented on the device for capillary velocity quantification. The frame rate was up to 450 frames per second, capable of distinguishing the velocity from 0 mm/s to ~0.5mm/s according to theoretical analyses. Eigen decomposition (ED) based capillary velocimetry was used to extract the blood flow speed information of the capillaries in human retina. Slow, medium and fast speed were identified and represented by the separated eigen values. Retinal and choriocapillaris layer were segmented to investigate the velocity of capillaries, including the superficial retinal layer, deep retinal layer and the whole retinal layer for retinal capillaries and choriocapillaris layer (~ 10 um thickness slab under Bruch’s membrane). All the subjects were imaged with the velocimetry scanning protocol. Color mapping was used to display the speed variations of blood flow
Fifteen young normal subjects were enrolled in the study. With the high lateral resolution, the choriocapillaris in the central macula were successfully captured and the lobular pattern clearly visualized. All the eyes showed the variations of blood flow speed on both retinal capillaries and the choriocapillaris. The separated eigen values successfully demonstrated the separated flow with fast, medium and slow speed. A faster flow was detected at retinal capillaries while the choriocapillaris showed a more flow heterogeneity with relatively slower speed (Figure 1)
Eigen decomposition based capillary velocimetry was successful to visualize the relative blood flow speed in capillaries on human retina and choriocapillaris. The modified scanning protocol is adaptable for implementation in commercially available SS-OCTA for the purpose of differentiating the blood flow speed in a certain range, particularly in capillaries. This velocimetry method may play an important role in not only studying the ocular disease but also in developing endpoints for therapeutic trials
This is a 2020 ARVO Annual Meeting abstract.
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