Non-invasive and high temporal resolution choroidal and retinal blood flow imaging using laser Doppler holography (Conference Presentation)

Abstract

Monitoring retinal vascularization is crucial to understand the pathophysiology of major diseases affecting the retina. Laser Doppler holography addresses the problem of temporal resolution in blood flow imaging. The method is conceptually close to laser Doppler flowmetry except it uses digital holography which allows for full-field imaging with a simple Mach–Zehnder interferometer. The light backscattered by the retina is combined with a reference field in order to measure the beat frequency spectrum with a very high acquisition frame rate. Wideband measurements of the optical Doppler broadening were performed with a 75 kHz crash test camera. The power spectrum density of the recorded holograms was analyzed with a short-time Fourier transform analysis to reveal local pulsatile flow. By using laser Doppler holography, we were able to image blood flow in vivo and qualitatively in retinal vessels with a temporal resolution down to a few milliseconds which enabled to investigate blood flow profiles in arteries and veins. Additionally the angiographic contrast in power Doppler images has proved sensitive to lateral flow which made possible to image vessels in en-face planes. Finally we showed that laser Doppler holography allows to reveal non-invasively in young and healthy subjects the large vessels of the choroid. To this end we stitched together multiple power Doppler images to form a wide-field laser Doppler holographic panorama.