Analysis of longitudinal sections of retinal vessels using Doppler OCT

We present a new method for imaging retinal vessels that provides both structural and hemodynamic information. Our technique enables measurements of absolute blood flow in retinal vessels with a single OCT sampling beam. The method is based on an OCT system with an integrated retinal tracker which can record 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.