Seven reasons for a uveitis specialist to understand the microbiome

The eye and the bowel could not be more disparate. The eye is compact, complex, and carefully arranged to shield itself from infection by virtue of its immune privilege. If the eye had a personality, certainly one might call it fastidious. By contrast, the gut is huge, by some perspectives a relatively simple tube, and designed to interact actively with the microbial world, the antithesis of the eye's design. If we were to anthropomorphize the gut, messy might be the first adjective to come to mind. Is it possible that inflammation inside the eye, uveitis, is somehow related to its cousin, the intestine, which is overrun with bacteria, fungi, viruses, archaea, and potentially other forms of microbial life? We believe that these two organs are actually very much connected. A collection of microorganisms lives on the surface of the eye, on the skin, in the mouth, and in every body orifice. But the preponderance of microorganisms is present in the intestine in anaerobic conditions. Most, but certainly not all, of what we know about the microbiome and immune-mediated disease concerns the gut microbiome. Consequently, in this essay, reference to the microbiome generally means microorganisms found in the intestine. Mouth, airway, skin, ocular surface, etc., are undoubtedly important, but in our opinion not yet linked as certainly to uveitis.