Abstract
We present a new method for imaging retinal vessels that provides both structural and hemodynamic information. Our technique is based on a single beam OCT system with an integrated retinal tracker that enables recording of arbitrary scan patterns. We record longitudinal sections along the traces of retinal vessels. The tracker function enables the acquisition of multiple longitudinal sections along the same trace to provide high-quality averaged OCT scans as well as temporal changes of flow dynamics. The vessel walls are clearly identified as narrow, bright lines from which the vessel diameter can be retrieved as a function of position along the vessel. Furthermore, the Doppler angle can be obtained at each position along the vessel trace, enabling measurement of absolute blood flow by Doppler OCT analysis. The method is demonstrated in flow phantoms and in-vivo on retinal vessel bifurcations in healthy volunteers. In 7 of 9 imaged bifurcations, measured in- and outflow deviate by less than 11%, demonstrating the consistency of the method.
Highlights
Alteration of retinal blood flow (RBF) is known to be associated with various ocular diseases such as glaucoma or diabetic retinopathy (DR) [1,2,3,4]
We report on a new approach to measure absolute blood velocity and flow in retinal vessels
The Optical coherence tomography (OCT) subsystem is based on a Michelson interferometer with polarization maintaining (PM) fibers
Summary
Alteration of retinal blood flow (RBF) is known to be associated with various ocular diseases such as glaucoma or diabetic retinopathy (DR) [1,2,3,4]. OCTA exploits the variations in the intensity and/or phase of the signals caused by motion of blood cells, which allows to differentiate vasculature from static tissue. While this method provides valuable information on the structure of retinal vasculature, quantitative information on blood flow cannot be directly retrieved. By recording two scans at the same position with a time delay in between, the axial velocity component of a moving blood cell can be retrieved from the phase difference of the signals [8]. To obtain the absolute velocity, the Doppler angle (angle between velocity vector and probing beam) has to be known
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