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Young-Joo Hong, Shuich Makita, Myeong-Jin Ju, Byeong Ha Lee, Yoshiaki Yasuno; Choroidal Blood Flow Imaging with High Penetration Doppler Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1245.
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Non-invasive choroidal blood flow dynamics study is useful for the safe and comfortable ophthalmic diagnosis. In this paper, high-speed and high-penetration Doppler optical coherence tomography (HSHP-OCT) using 1 µm probe beam demonstrates bi-directional blood flow imaging in the deep choroid.
12 normal eyes of 6 subjects were scanned by HSHP-OCT. The HSHP-OCT is a custom-built prototype system with 1 µm probe wavelength, which enables high penetration to the deep choroid/sclera. Swept-source OCT with a short cavity laser enables very small signal degradation even in the region far from the reference line of OCT. The depth resolution was 6.38 µm in tissue, and sensitivity was 99.34 dB at 0.4 mm from the reference line. The 3 x 3mm areas of macula and optic nerve head (ONH) were scanned with 1024 x 256 A-lines. The scanning speed was 100,000 A-lines/s, and it took 3.3 seconds per volume. In order to enhance the sensitivity of bi-directional blood flow measurement, a custom made OCT phase stabilization algorithm was applied. Maximum and minimum measurable axial blood flow speeds are estimated to be 26.4 mm/s and 2.83 mm/s at a signal-to-noise ratio of 30 dB.
In ONH area, bi-directional blood flow is observed in the retina and choroid in all 12 eyes, while, in macular area, blood flow was clearly observed in choroid in 5 of 12 eyes. Figure shows representative Doppler tomographies and corresponding OCT images. In Fig. (c), clear flow can be seen beneath myopic conus, these were observed in 4 of 6 eyes with myopic conus. In Fig. (f), a thick blood vessel penetrating into lamina cribrosa can be seen. The blood flow within/beneath the lamina cribrosa observed in 5 of 12 eyes. In Fig. (i) 3 choroidal blood vessels and 1 pair of bi-directional blood flow can be seen.
The HSHP-OCT could give us the bi-directional blood flow information at the choroid, beneath myopic conus and lamina cribrosa. It could help the ophthalmic diagnosis related to the ocular circulation.
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