Influence of smoking on the human ocular surface microbiome and tear proteome.

The ocular surface hosts microbes of low abundance and their genomes, collectively called the ocular surface microbiome (OSM). The OSM is involved in maintaining health and protecting the eye from infection. Although disruption of this microbial balance has been linked to various eye diseases, the effect of smoking, a known risk factor for ocular conditions, on the OSM remains unclear. We analysed ocular samples from smokers (n = 17) and non-smokers (n = 24) using metagenomic sequencing and proteomics approaches to assess both microbial composition and functions, as well as the host protein profiles. Microbial DNA was examined for bacterial, fungal, and viral taxa, with contaminants removed using microDecon. Statistical analyses showed no significant differences in microbial diversity or tear proteins between groups, apart from one bacterial gene. No bacterial, fungal, or viral species were uniquely associated with smoking status. While no clear smoking-related effects were observed in microbial communities or tear proteome composition, the overall stability of tear proteins may reflect intrinsic resilience dynamics that maintain low microbial abundance on the ocular surface.