Retinal oxygen metabolism in healthy subjects and glaucoma patients.

BACKGROUND: To test whether retinal oxygen metabolism is different in glaucoma patients compared with healthy subjects.
METHODS: This was a two-centre study where retinal vessel oxygen saturation was measured in glaucoma patients and healthy individuals with a non-invasive spectrophotometric retinal oximeter. Visual fields were obtained in the glaucoma patients.
RESULTS: No statistical difference was found in retinal oxygen saturation in arterioles (p=0.16), venules (p=0.16) and arteriovenous difference (p=0.24) when all glaucoma patients (n=74) were compared with healthy individuals (n=89). When patients with advanced glaucoma (visual field mean defect (MD ≥ 10 dB, n=21)) were compared with healthy individuals, the oxygen saturation in venules was higher in glaucoma patients (58.2% ± 5.4% vs 53.8% ± 6.4%; p=0.0054, mean ± SD) and the arteriovenous difference was lower in glaucoma patients (36.4% ± 4.7% vs 39.5% ± 5.7%; p=0.021). In glaucoma patients with mild glaucoma (visual field MD ≤ 5 dB, n=33), no statistical differences were found in retinal oxygen saturation compared with healthy individuals.
CONCLUSIONS: Glaucoma patients with advanced glaucoma have higher oxygen saturation in venules and lower arteriovenous difference in oxygen saturation compared with healthy individuals. The decreased arteriovenous difference in severe glaucoma may be related to lower oxygen consumption secondary to neuropathy.