Visible light optical coherence tomography angiography (vis-OCTA) and local microvascular retinal oximetry in human retina

Abstract

We report herein the first visible light optical coherence tomography angiography (vis-OCTA) for human retinal imaging. Compared to the existing vis-OCT systems, we devised a spectrometer with a narrower bandwidth to increase the spectral power density for OCTA imaging, while retaining the major spectral contrast in the blood. We achieved a 100 kHz A-line rate, the fastest acquisition speed reported so far for human retinal vis-OCT. We rigorously optimized the imaging protocol such that a single acquisition takes <6 seconds with a field of view (FOV) of 3x7.8 mm 2 . The angiography enables accurate localization of microvasculature down to the capillary level and thus enables oximetry at vessels < 100 μm in diameter. We demonstrated microvascular hemoglobin oxygen saturation (sO2) at the feeding and draining vessels at the perifoveal region. The longitudinal repeatability was assessed by <5% coefficient of variation (CV). The unique capabilities of our vis-OCTA system may allow studies on the role of microvascular oxygen in various retinal pathologies.

High-resolution functional photoacoustic monitoring of vascular dynamics in human fingers

“…OCTA can also estimate the flow and sO 2 of the microvessels by using the Doppler effect and visible light spectroscopy [ 13 , 14 ]. However, although sO 2 measurement using OCTA has been reported in human eye vessels [ 15 ], it has not yet been measured through the skin, due to the modality’s limited penetration depth [ 12 ]. Even when light passes through blood vessels and then bounces back from the tissues, OCTA registers the signal changes created by the blood vessels, which creates “false” blood vessels called OCTA projection artifacts that can affect clinical assessment [ 16 ].…”