Retinal Oximetry Revealed Glaucomatous Eyes Had Lower Retinal Metabolism Using Visible Light Optical Coherence Tomography (vis-OCT)

Abstract

Purpose : To compare in vivo measurements of oxygen saturation (sO₂) between healthy and glaucomatous eyes using visible-light optical coherence tomography (vis-OCT).

Methods : Eight eyes of 8 healthy volunteers and five eyes of 5 glaucoma age-matched patients were enrolled into our pilot study. For each eye, one pair of retinal major artery and vein in superior and inferior regions near the optic nerve head (Figure) were scanned during the same session with our prototype vis-OCT (8192 x 16 samplings in 1x1mm²). Spectroscopic analysis was performed using short-time Fourier transformation (STFT). Wavelength-dependent OCT amplitudes from the same depth location across adjacent A-lines, all within the blood vessels, were averaged and then fitted to hemoglobin absorption profile based on Beer-Lambert’s law. Highest artery and vein sO₂ values in superior or inferior regions were recorded as the sO₂ measurements for each eye. Wilcoxon’s paired signed rank test was used to compare the age-matched healthy and glaucomatous subjects. Correlation between vein sO₂ and visual field mean deviation (MD) recorded at the same visits was calculated using Spearman correlation coefficient (r). Results were compared with conventional structural OCT measurements, retinal nerve fiber layer (RNFL) and ganglion cell inner plexiform layer (GCIPL) thickness measured using Cirrus HD-OCT (Zeiss, Dublin, CA).

Results : Table 1 and Table 2 show demographics and measurements on 5 age-matched pairs of healthy and glaucomatous eyes. Artery sO₂ showed no difference between healthy and glaucomatous eyes, while vein sO₂ was marginally higher in glaucomatous eyes than healthy eyes (Table 2). Vein sO₂ and RNFL and GCIPL thicknesses all showed statistically significant correlation with MD (Table 3). When comparing the correlation between vein sO2, RNFL and GCIPL, no statistical difference was detected between any combination (Fisher’s paired test).

Conclusions : Glaucomatous eyes had marginally higher oxygen saturation in the veins compared to healthy eyes, while there was no difference in oxygen saturation in the arteries, suggesting less oxygen consumption in the retina with glaucomatous damage. Vis-OCT sO₂ measurement may have a potential as a clinical glaucoma biomarker in parallel with RNFL and GCIPL thickness. Further study with a larger sample size is warranted.

This is a 2021 ARVO Annual Meeting abstract.