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Scott Lawrence, Pooja Jani, Kyle Billow, Jean-Claude Mwanza, Iryna Falkenstein; Retinal Oximetry in Early Primary Open Angle Glaucoma. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4464.
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To determine if there is a difference in retinal oxygen saturation in eyes diagnosed with early primary open angle glaucoma (POAG) versus normal eyes.
This was a prospective observational study. Twenty eyes (13 patients) diagnosed with early POAG (visual field mean deviation < -6 dB; mean, -2.83 ± 1.19 dB) underwent retinal oximetry measurement. Twenty normal eyes (20 patients) served as controls. Optic disc-centered images were obtained with the Oxymap T1 retinal oximeter (Oxymap, Reykjavik, Iceland) for all patients. Mean retinal oxygen saturation was calculated for each eye globally and by quadrant (inferonasal, IN; superonasal, SN; inferotemporal, IT; superotemporal, ST) using a modified ring algorithm developed at our institution. Glaucoma patients also underwent Humphrey visual field, 24-2 testing and peripapillary retinal nerve fiber layer (RNFL) measurement using spectral domain optical coherence tomography. Retinal oxygen saturation levels were compared between groups using general linear model analysis after adjusting for age. The correlation between retinal oxygen saturation, RNFL and visual field mean deviation was assessed with Pearson correlation.
Oxygen saturation in venules (SvO2) was higher in eyes diagnosed with early POAG compared to normal eyes (mean, 61.94 ± 2% vs 51.39 ± 2%, p = 0.002). SvO2 was also elevated in each quadrant in the early POAG group (IN, p < 0.001; SN, p = 0.03; IT, p = 0.005; ST, p = 0.03). The mean arteriovenous difference was lower in early POAG eyes (28.9 ± 2% vs 37.84 ± 2%, p = 0.001) and in all quadrants. There was no difference in mean (p = 0.39) or quadrant (all p > 0.05) arteriolar oxygen saturation between groups, and there was no correlation between mean retinal oxygen saturation and mean RNFL thickness (r = 0.06) or visual field mean deviation (r = 0.08).
Patients with early POAG have significantly elevated SvO2 and decreased arteriovenous difference in retinal oxygen saturation compared with normal eyes. These preliminary findings suggest decreased retinal oxygen utilization and metabolism in eyes with mild glaucomatous changes.
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