Retinal Oximetry Based on Nonsimultaneous Image Acquisition Using a Conventional Fundus Camera

To measure the retinal arteriole and venule oxygen saturation (SO
₂
) using a conventional fundus camera, retinal oximetry based on nonsimultaneous image acquisition was developed and evaluated. Two retinal images were sequentially acquired using a conventional fundus camera with two bandpass filters (568 nm: isobestic, 600 nm: nonisobestic wavelength), one after another, instead of a built-in green filter. The images were registered to compensate for the differences caused by eye movements during the image acquisition. Retinal SO
₂
was measured using two wavelength oximetry. To evaluate sensitivity of the proposed method, SO
₂
in the arterioles and venules before and after inhalation of 100% O
₂
were compared, respectively, in 11 healthy subjects. After inhalation of 100% O
₂
, SO
₂
increased from 96.0 ± 6.0% to 98.8% ± 7.1% in the arterioles (
p
= 0.002) and from 54.0 ± 8.0% to 66.7% ± 7.2% in the venules (
p
= 0.005) (paired t-test,
n
= 11). Reproducibility of the method was 2.6% and 5.2% in the arterioles and venules, respectively (average standard deviation of five measurements,
n
= 11).