Purpose:
To visualize retinal and choroidal vessels and abnormal vasculature non-invasively by high-sensitive Doppler optical coherence angiography.
Methods:
High-speed spectral-domain OCT with double probing beams is used. Doppler frequency shift is obtained from the phase shift between two OCT signals acquired by each probing beam at the same location, but the different time position. This system is operated at 27,000 axial scans per second. An imaging area of 7.7 × 7.7 mm was scanned within 5 seconds. The minimum detectable axial blood flow is 55 µm/s at signal-to-noise ratio of 15 dB. Three-dimensional blood flow distribution with slow blood flow velocity will be detected. High-sensitive Doppler optical coherence angiography (HS-DOCA) was performed for 10 eyes of 5 subjects without marked posterior abnormalities and 3 eyes of polypoidal choroidal vasculopathy (PCV). The retinal and choroidal vasculature was divided based on the location of the retinal pigment epithelium segmented by OCT images. En-face projection images of the retinal and choroidal blood flow distribution in PCV are compared with other modalities.
Results:
In 10 of the 10 eyes without abnormalities, major retinal vessels and narrow retinal arterioles were visualized in retinal en-face projections, and vasculature of small choroidal vessesls were observed in choroidal en-face projections. In 3 of the 3 eyes of PCV, vascular network was observed in choroidal en-face projections. In 3 of 3 eyes, the vascular patterns of these projections were corresponded to those in Indocyanine green angiography as shown in Figure.
Conclusions:
High-sensitive Doppler OCA can visualize vasculature of small retinal and choroidal vessels, and be used to detect abnormal vessels in PCV non-invasively.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • choroid: neovascularization • blood supply