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

To measure the retinal arteriole and venule oxygen saturation (SO₂) 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 SO₂ was measured using two wavelength oximetry. To evaluate sensitivity of the proposed method, SO₂ in the arterioles and venules before and after inhalation of 100% O₂ were compared, respectively, in 11 healthy subjects. After inhalation of 100% O₂, SO₂ 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).