Microbiome of the Ocular Surface: Resident or Transient Ecosystem?

The ocular surface microbiome (OSM) is a low-density, low-diversity microbial ecosystem influenced by host and environmental factors, including age, hygiene, contact lens use, and systemic disease. Unlike other mucosal sites, the eye lacks a well-defined core microbiome, and its microbial composition varies significantly between individuals. Advances in metagenomics have revealed that commensals such as  and  may contribute to immune regulation and homeostasis. Dysbiosis has been linked to ocular surface disorders, such as dry eye disease (DED), allergic conjunctivitis (AC), and contact lens-related inflammation, with shifts in microbial abundance and diversity. Continued research is needed to define resident versus transient species and to develop microbiome-based diagnostics and therapies.