Purpose:
Spectral domain optical coherence tomography (SD-OCT) provides structural and flow (Doppler signal) tomographies. But Doppler detection of current OCT is unable to properly image choroidal vasculature. We here demonstrate extended visualization of in vivo human choroidal vasculature by high-penetration and high-sensitive Doppler optical coherence angiography (HPHS-DOCA). HPHS-DOCA uses 1 µm wavelength, offering higher penetration than standard 840 nm OCT. High-sensitive Doppler detection is achieved by double beam OCA scheme.
Methods:
Ten eyes of 5 normal subjects were examined by HPHS-DOCA (wavelength: 1.02 µm, depth resolution: 4.4 µm in tissue, acquisition rate: 47 kHz). HPHS-DOCA scans the retina with two beams creating two spots on the retina with 162 µm spatial separation. These two spots scan the same location with a time separation of 1.1 ms. After signal processing, we have two Doppler velocity tomographies: high-sensitive slow-velocity-tomography (0.03<v<0.18 mm/s) and conventional Doppler tomography (2.7<v<8.7 mm/s). En-face Doppler power projection images are obtained for choroidal vasculature from macula to optic nerve head (ONH). To evaluate high-penetration capability of HPSH-DOCA, eyes were also scanned by HS-DOCA with a standard wavelength (840 nm).
Results:
A larger number of choroidal vessels are observed in high-sensitive Doppler image than in conventional Doppler images (7 of 10 eyes). In particular, small flow vessels with low interweaving are seen around ONH (see figure). By comparing images with those acquired at standard wavelength HS-DOCA around the ONH, improved visualization of choroidal vessels with HPHS-DOCA is evident.
Conclusions:
HPHS-DOCA enhances choroidal vasculature visibility. Compared to 840 nm system, deeper vessels are detectable. Improved visualization of choroidal vasculature may be an asset in screening and diagnosing choroidal pathologies.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • choroid • choroid: neovascularization