Retinal Vascular Oxygen Saturation in Primary Open-Angle Glaucoma: A Systematic Review and Meta-Analysis

Systematic Review and Meta-Analysis of Retinal Vascular Oxygen Saturation in Primary Open-Angle Glaucoma (POAG).

To evaluate alterations in retinal arterial oxygen saturation (AO₂S), venous oxygen saturation (VO₂S), and the arteriovenous (A-V) difference among patients with POAG.

A systematic literature search was conducted in PubMed, Scopus, and EMBASE databases up to June 11, 2025 (PROSPERO: CRD42025633571). Eligible studies reported retinal vascular oxygen saturation parameters in POAG and healthy control groups. Extracted outcomes included AO₂S, VO₂S, and A-V oxygen saturation difference. Meta-analysis was performed using random-effects models, with Hedges' g applied to calculate standardized mean differences (SMDs) and corresponding 95% confidence intervals (CIs). Subgroup analysis was conducted based on measurement methodology. Risk of bias and certainty of evidence were evaluated using the Newcastle-Ottawa Scale and the GRADE framework, respectively.

Nine studies involving 883 participants (488 patients [511 eyes] with POAG and 395 healthy controls [399 eyes]) were included. Pooled analysis demonstrated a significant elevation in AO₂S and VO₂S in POAG eyes compared with controls (SMD = 0.37; 95% CI: 0.06 to 0.68; P = 0.019; SMD = 0.58; 95% CI: 0.29 to 0.88; P < 0.001), respectively. In contrast, A-V difference showed no significant alteration between groups (SMD = -0.26; 95% CI: -0.58 to 0.06; P = 0.116). Subgroup analyses revealed that both AO₂S and VO₂S were elevated when measured with dual-wavelength oximetry, whereas hyperspectral imaging showed increased VO₂S but no significant alteration in AO₂S.

POAG demonstrated elevated retinal vascular O2 saturation, which may reflect reduced retinal oxygen consumption due to structural damage and/or altered vascular regulation. Findings are consistent with vascular-metabolic involvement in glaucoma and suggest retinal oximetry is a promising noninvasive biomarker warranting further prospective validation.