Macular Oxygen Saturation in Glaucoma Using Retinal Oximetry of Visible Light Optical Coherence Tomography

Oxygen saturation (sO₂) plays a critical role in retinal pathophysiology, especially at the macula, which undergoes significant energy consumption. While macular damage has been suggested to be involved in early-stage glaucoma, there has been no report to date on non-invasive macular sO₂ in glaucoma. Therefore, we conducted this study to compare macular sO₂ associated with other clinical measurements between normal and glaucoma subjects and evaluate whether there are significant differences.

This is a cross-sectional study. We used visible light optical coherence tomography (VIS-OCT) for retinal oximetry in perifoveal vessels. The subjects from groups of normal, suspect/pre-perimetric glaucoma (GS/PPG) and perimetric glaucoma (PG) were scanned using VIS-OCT in the macular region with a sampling density of 512×256 in an area of 5×5 mm². 48 eyes (16 normal, 17 GS/PPG and 15 PG) were included for the analysis. For each eye, we measured the sO₂ of arterioles (AsO₂), venules (VsO₂), and calculated the difference between arterioles and venules (A-V sO₂=AsO₂-VsO₂), oxygen extraction (OE=(AsO₂-VsO₂)/AsO₂ ×100%). Additionally, we included Zeiss Cirrus OCT scans and 24-2 visual field test (VFT) for clinical benchmark. One-way ANOVA was used to compare the differences among the three groups. Spearman correlation tests were used for correlation sO₂ markers to standard metrics including the thickness of ganglion cell layer and inner plexiform layer (GCL+IPL), circumpapillary retinal nerve fiber layer (cpRNFL) and mean deviation (MD) in VFT.

Significant differences were found among three groups for all VIS-OCT, Zeiss OCT, and VFT variables. Macular AsO₂, A-V sO₂, OE decreased, and VsO₂ increased along with severity. Macular AsO₂ and A-V sO₂ were statistically correlated with GCL+IPL and cpRNFL in all eyes, as well as only PG eyes. Within PG eyes, the correlation between AsO₂ and GCL+IPL is dominant in more damaged lower hemifield.

The GS/PPG and PG subjects had significantly higher macular VsO₂, lower A-V sO₂ and OE indicating less oxygen consumption. The sO₂ measured by retinal oximetry of VIS-OCT can be a potential metric for the early diagnosis of glaucoma.