Volumetric and quantitative imaging of retinal blood flow in rats with optical microangiography

In this paper, we present methods for 3D visualization and quantitative measurements of retinal blood flow in rats by the use of optical micro angiography imaging technique (OMAG). We use ultrahigh sensitive OMAG to provide high-quality 3D RBF perfusion maps in the rat eye, from which the Doppler angle, as well as the diameters of blood vessels, are evaluated. Estimation of flow velocity (i.e. axial flow velocity) is achieved by the use of Doppler OMAG, which has its origins in phase-resolved Doppler optical coherence tomography. The measurements of the Doppler angle, vessel size, and the axial velocity lead to the quantitative assessment of the absolute flow velocity and the blood flow rate in selected retinal vessels. We demonstrate the feasibility of OMAG to provide 3D micro angiograms and quantitative assessment of retinal blood flow in a rat model subjected to raised intra-ocular pressure (IOP). We show that OMAG is capable of monitoring the longitudinal response of absolute blood velocity and flow rate of retinal blood vessels to increased IOP in the rat, demonstrating its usefulness for ophthalmological research.