Relationship between oxygen saturation of the retinal vessels and visual field defect in glaucoma patients: comparison with each hemifield

Abstract

Purpose: This study aimed to elucidate the relationship between visual field defects in the upper and lower hemifields and the corresponding oxygen saturation of the retinal vessels in patients with glaucoma. Methods: Patients with glaucoma (n = 44) exhibiting more than a 10 dB difference between the upper and lower total deviation (TD) were enrolled in the study. After measuring the retinal vessel oxygen saturation by a non-invasive spectrophotometric retinal oximeter, the hemifields in one eye of each patient were divided into worse (worse TD) and better (better TD) hemifield areas. We additionally evaluated a separate group of 40 patients with glaucoma who exhibited less than a 5 dB difference between the upper and lower TD. Statistical analysis was performed using a Student's t-test. Results: A higher mean venous saturation of oxygen (SaO2) was observed in the worse (59.0 ± 8.0%) hemifield compared to the better (55.4 ± 7.2%) hemifield (p < 0.01). The mean arteriovenous difference in the SaO2 was lower in the worse (44.4 ± 9.0%) hemifield compared to the better (48.6 ± 11.4%) hemifield (p = 0.02). However, when we evaluated the worse and better hemifields in the patients who had less than a 5 dB difference in the upper and lower hemifield TD, we found no statistically significant differences for either the retinal SaO2 in the venous vessels or the arteriovenous difference. Conclusions: Advanced glaucomatous visual field defects were associated with increased SaO2 in the venous vessels and a decreased arteriovenous difference in the SaO2. The present results suggest there is a reduced retinal oxygen extraction in eyes with glaucomatous damage due to retinal ganglion cell loss.