Retinal blood flow reversal quantitatively monitored in out-of-plane vessels with laser Doppler holography

TL;DR

This paper introduces a digital method using laser Doppler holography to visualize and quantify blood flow direction and reversals in retinal vessels, enhancing non-invasive ophthalmic imaging.

Contribution

The study presents a novel Doppler spectrum asymmetry technique to determine local blood flow direction in out-of-plane retinal vessels with high temporal resolution.

Findings

Successfully visualized flow moving towards and away from the camera.

Quantitatively monitored pathological blood flow reversals.

Enhanced understanding of retinal blood flow dynamics.

Abstract

Laser Doppler holography is a planar blood flow imaging technique recently introduced in ophthalmology to image human retinal and choroidal blood flow non-invasively. Here we present a digital method based on the Doppler spectrum asymmetry that reveals the local direction of blood flow with respect to the optical axis in out-of-plane vessels. This directional information is overlaid on standard grayscale blood flow images to depict flow moving towards the camera in red and flow moving away from the camera in blue, as in ultrasound color Doppler imaging. We show that thanks to the strong contribution of backscattering to the Doppler spectrum in out-of-plane vessels, the local axial direction of blood flow can be revealed with a high temporal resolution, which enables us to evidence pathological blood flow reversals. We also demonstrate the use of optical Doppler spectrograms to quantitatively monitor retinal blood flow reversals.