Measuring oxygen saturation in retinal and choroidal circulations in rats using visible light optical coherence tomography angiography

Visible light optical coherence tomography (vis-OCT) has demonstrated its capability of measuring vascular oxygen saturation (sO(2)) in vivo. Enhanced by OCT angiography, the signal from microvasculature can be further isolated and directly used for sO(2) extraction. In this work, we extended the theoretical formulation for OCT angiography-based oximetry by incorporating the contribution from motion contrast enhancement. We presented a new method to eliminate the associated confounding variables due to blood flow. First, we performed in vitro experiments to verify our theory, showing a stable spectral derivative within the selected wavelength bands for sO(2) extraction. Then, we tested our method in vivo to measure retinal sO(2) in rats inhaling different gas mixtures: normal air, 5% CO2, pure O-2, and 10% O-2. Absolute sO(2) values in major arterioles and venules in the retinal circulation can be accurately measured. In addition, we demonstrated the relative changes of sO(2) can be measured non-invasively from choriocapillaris immediately underneath the retinal pigmented epithelium (RPE) in rodents. (C) 2015 Optical Society of America