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Boy Braaf, Koenraad A. Vermeer, Kari V. Vienola, Victor Arni D. P. Sicam, Johannes F. de Boer; Double-Scanning to Visualize the Retinal Micro-Vasculature with Phase-Resolved Optical Frequency Domain Imaging. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2205.
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To visualize the retinal micro-vasculature with phase-resolved optical frequency domain imaging (OFDI).
A scan-pattern was developed for a two-fold scanning of retinal structures with high location stability. This method enabled phase-resolved OFDI imaging with a long time-delay which enhances the visualization of blood flows with a low flow velocity component parallel to the OCT-bundle. This technique was implemented in a 1-μm OFDI system from an earlier study (Braaf et al., Optics Express 2011) with custom phase-stabilization software for imaging of blood flow. The macula of a healthy volunteer was scanned over an area of 3 mm x 3 mm with a time-delay of 2.48 ms between two B-scans at the same location to visualize blood flows with velocities down to 0.4 mm/s for an 89° angle of incidence.
The retinal micro-vasculature was successfully visualized around the foveal avascular zone (Fig. 1) by integration of the absolute phase difference at every location. Several small arteries and veins as well as arterioles and venules can be resolved for vessel diameters down to 40 μm. A cross-sectional intensity image (Fig. 2) is shown with the retinal blood flow marked in red. This image clearly shows the cross-sectional visualization of the numerous vessels that are observed in figure 1. This type of vascular imaging is clinically relevant for the screening of ocular pathologies with early micro-vasculature changes.
The retinal micro-vasculature can be imaged with OFDI using the double-scanning method.
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