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Kazuhiro Kurokawa, Young-Joo Hong, Shuichi Makita, Yoshiaki Yasuno; In Vivo Choroidal Micro-vasculature Imaging by High-penetration Optical Coherence Angiography. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3161.
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© ARVO (1962-2015); The Authors (2016-present)
High-penetration optical coherence tomography (HP-OCT) with extended OCT angiography method is developed for noninvasive angiography. Its ability to image choroidal micro-vasculature in the choroidal capillary and Sattler’s layer is assessed.
Six dominant eyes of 6 healthy subjects were examined. The eyes were scanned by a custom built HP-OCT, which uses 1-μm swept laser source. The macula region (1.5 mm x 1.5 mm) was imaged. Ten volumes were acquired for each eye, and 5 volumes were used for the processing. In order to obtain enhanced angiographic contrast, we proposed the multiple volume processing method. Averaged intensity, averaged power of Doppler shift (averaged Doppler), and averaged amplitude correlation coefficient were calculated from multiple OCT volumes taken at the same macular region. The Doppler shift and amplitude correlation coefficient were calculated between adjacent B-scans. Finally, en face projections were created for two regions beneath the retinal pigment epithelium (RPE); one is a layer of the choroid from RPE/choroid junction to 35-μm depth in choroid (Ch1), and the other is from 35-μm to 70-μm depth (Ch2).
The angiographic images showed the choroidal micro-vasculature in all eyes. The representative images of a subject are shown in Figs. The averaged intensity images are shown in Figs.(a) and (b). The averaged Doppler images are shown in Figs.(c) and (d). The amplitude decorrelation images are shown in Figs.(e) and (f). The color composite images with averaged intensity and average Doppler images are shown in Figs.(g) and (h). The micro-vascular network was well observed by an averaged Doppler than the others. Scattering image does not clearly show the vascular network, because both the micro-vasculature and surrounding tissue appeared with hyper-scattering.
The combination of HP-OCT and the enhanced OCT angiographic method is useful for the detection of the choroidal micro-vasculature. Especially, the averaged power of Doppler phase-shift was found to be useful to visualize choroidal micro-vasculature in the choroidal capillary and Sattler’s layer.
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