Compositional disparities and potential pathogenic mechanisms of the ocular microbiome in cataract patients: insights from high-throughput sequencing

Cataract remains the leading cause of blindness worldwide, however, whether the ocular microbiome plays a role in its pathogenesis remains unclear. We characterized ocular surface and intraocular microbiome in cataract patients via high-throughput 16 S rRNA gene sequencing. Samples included anterior capsule of lens (ACL), aqueous humor (F), and conjunctival sac (C) from cataract patients, along with conjunctival swabs from healthy controls (N). Microbial diversity and community structure were assessed via alpha diversity indices, principal component analysis (PCA), Venn diagrams, and Circos plots; differential species were identified with linear discriminant analysis effect size (LEfSe), and functions were predicted via the Functional Annotation of Prokaryotic Taxa (FAPROTAX) database. Although ocular surface diversity was comparable between cataract patients and controls, patients showed increased colonization by opportunistic pathogens. Among the group ACL, group F, and group C, Exiguobacterium indicum was the only high-abundance species shared. Notably, ACL samples exhibited a distinct enrichment of Cyanobacteria. Functional predictions indicated enhanced nitrogen metabolism, methylated compound utilization, and inorganic carbon metabolism in intraocular microbiome, with several species potentially dependent on host cellular resources. These findings reveal striking compositional and functional disparities between ocular surface and intraocular microbiome and suggest that intraocular Cyanobacteria enrichment may contribute to cataract development.