Ambient Air Pollution and Glaucoma: A Systematic Review and Meta-analysis of Observational Studies

Glaucoma is a leading cause of irreversible blindness worldwide, and environmental risk factors beyond intraocular pressure (IOP) are increasingly being investigated. Ambient air pollution, particularly fine particulate matter (PM₂.₅), may contribute to glaucomatous optic neuropathy through oxidative stress and vascular dysregulation; however, existing evidence remains fragmented.

To systematically review and quantitatively synthesize the association between ambient air pollution exposure and glaucoma risk, IOP, and structural markers of glaucomatous optic neuropathy.

This systematic review and meta-analysis followed PRISMA 2020 guidelines and was registered with PROSPERO. PubMed and Embase were searched from inception to 30^th December 2025, for observational studies evaluating ambient air pollution exposure and glaucoma-related outcomes. Random-effects meta-analysis using generic inverse-variance methods was conducted for studies reporting associations between long-term PM₂.₅ exposure and glaucoma. Other pollutants were synthesized narratively.

Eighteen observational studies from diverse geographic regions were included, of which eight contributed to the PM₂.₅ meta-analysis. Higher long-term PM₂.₅ exposure was associated with an increased risk of glaucoma (pooled RR = 1.12; 95% CI, 1.06-1.18), with moderate heterogeneity (I² = 78.7%). Associations for NO₂, NOx, PM₁₀, and CO were directionally positive but heterogeneous. Structural changes, including RNFL and GCIPL thinning, and modest IOP elevations were also reported.

Long-term PM₂.₅ exposure is associated with increased glaucoma risk, suggesting a potential environmental contribution; however, causality cannot be established from the available observational evidence. These findings highlight the need to integrate ocular outcomes into environmental health policy and to prioritize prospective studies capable of addressing confounding and temporality.