Ocular surface microbiota in primary open angle glaucoma

Primary open-angle glaucoma (POAG) is a leading cause of irreversible blindness, yet the contribution of the ocular-surface (OS) microbiota remains poorly defined. We conducted a cross-sectional study including 27 POAG patients on chronic hypotensive therapy and 119 healthy Italian controls, profiled by 16S rRNA amplicon sequencing (Ion GeneStudio S5) and analyzed with QIIME2/phyloseq. POAG samples showed higher α-diversity (Shannon 4.23 vs 2.77; Observed richness 407 vs 154; Wilcoxon q < 1 × 10 ⁻⁹) and a distinct β-diversity profile (PERMANOVA p = 0.001; R ² = 0.104). Compositional shifts included depletion of Firmicutes with loss of Staphylococcus in controls’ place, and enrichment of Proteobacteria (e.g., Pseudomonas) together with unclassified Enterobacterales and a larger unclassified fraction. Differential-abundance testing identified numerous significant taxa separating groups, consistent with a more diverse yet less defined microbiota in POAG. These findings indicate an ocular-surface dysbiosis associated with POAG in a treatment-exposed cohort, supporting the relevance of host–microbe interactions and motivating longitudinal, treatment-naïve and functional studies before causal or translational inferences.