Spectral oximetry assessed with high-speed ultra-high-resolution optical coherence tomography

Abstract

We use Fourier domain optical coherence tomography (OCT) data to assess retinal blood oxygen saturation. Three-dimensional disk-centered retinal tissue volumes were assessed in 17 normal healthy subjects. After removing DC and low-frequency a-scan components, an OCT fundus image was created by integrating total reflectance into a single reflectance value. Thirty fringe patterns were sampled; 10 each from the edge of an artery, adjacent tissue, and the edge of a vein, respectively. A-scans were recalculated, zeroing the DC term in the power spectrum, and used for analysis. Optical density ratios (ODRs) were calculated as ODR[subscript Art] = ln(Tissue[subscript 855]/Art[subscript 855])/ln(Tissue[subscript 805]/Art[subscript 805) and ODR[subscript Vein] = ln(Tissue[subscript 855]/Vein[subscript 855])/ln(Tissue[subscript 805]/Vein[subscript 805]) with Tissue, Art, and Vein representing total a-scan reflectance at the 805- or 855-nm centered bandwidth. Arterial and venous ODRs were compared by the Wilcoxon signed rank test. Arterial ODRs were significantly greater than venous ODRs (1.007 ± 2.611 and −1.434 ± 4.310, respectively; p = 0.0217) (mean±standard deviation). A difference between arterial and venous blood saturation was detected. This suggests that retinal oximetry may possibly be added as a metabolic measurement in structural imaging devices.