Next-generation sequencing (NGS) studies of healthy canine eyes have discovered a more diverse and distinct bacterial microbiota compared to culture-based techniques. Little is known about the canine ocular surface microbiome and its impact on disease. The objective of this project is to characterize the composition and function of the canine ocular surface microbiome in the context of a common, naturally occurring ocular disease. We aim to compare the ocular surface microbiota in dogs with keratoconjunctivitis sicca (KCS) to control dogs free of ocular disease. Conjunctival swabs will be obtained from privately owned dogs with informed consent. Genomic DNA will be extracted from the swabs and processed to construct metagenomic shotgun sequencing libraries on an Illumina platform. Data will be analyzed using Quantitative Insights Into Molecular Ecology (QIIME2). Alpha and beta diversity metrics will be compared between diseased and healthy eyes to assess differences in species richness, evenness, composition, and abundance. All taxa will be tested for differential abundance between groups. The relationship between the microbiome composition and functional gene differences on the ocular surface of dogs with KCS will be examined. We expect to find significant alterations in diversity and abundance (dysbiosis) in the canine ocular surface microbiome of diseased eyes compared to healthy eyes. Improving our understanding of how the canine ocular surface microbiome contributes to the pathogenesis and/or increased risk of KCS will allow for future insights into novel treatments or preventative approaches.