The Gut–Eye Axis: Correlation Between the Gut Microbiota and Autoimmune Dry Eye in Individuals With Sjögren Syndrome

ABSTRACT: The impact of gut microbiota on human health, autoimmunity, and disease occurrence has long been recognized since the advancement of metagenomic sequencing technology has enabled a new level of perspective on the human microbiome. Emerging findings also suggest the existence of a gut-eye axis, wherein gut dysbiosis may be a crucial factor affecting the onset and progression of multiple ocular diseases. Sjögren syndrome (SS) is a chronic autoimmune disease mainly affecting the exocrine glands, primarily the lacrimal gland in the eye, resulting in severe dry eye. Although there are currently various treatments for environmental dry eye, the efficacy for SS-related autoimmune dry eye is limited, and new and more effective therapies still need to be explored. The latest studies have demonstrated that the gut microbiota plays a key role in the pathogenesis of autoimmune dry eye. This review describes the effect of gut microbiota on the ocular surface of autoimmune dry eye; introduces the presumable pathways forming the "gut dysbiosis-ocular surface-lacrimal gland axis"; discusses the advantages of restoring intestinal microecology to treat dry eye by fecal microbiota transplantation or probiotics, which are expected to provide perspectives into the correlation between the gut microbiome and dry eye; enhance our understanding of the pathogenesis in autoimmune dry eye; and be useful in the development of future interventions of dry eye by regulating the gut microbiota.