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

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

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

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.