Glaucoma and the Human Microbiome

Abstract

Purpose of Review: To explore a view of the human microbiome as an interconnected, functional, dynamic system that may be linked to the pathogenesis and progression of glaucoma. Methods: A literature review was undertaken that included publications from 1966 to 2023. Results: Bacterial lipopolysaccharides (LPS) activate toll-like receptors (TLR) and mediate the human immune response. The LPS-TLR4 pathway is a potential avenue for the ocular, gut, and oral microbiomes to interface and/or influence ocular disease. Studies of gut dysbiosis have shown that alterations in the healthy microbiota can predispose the host to immune-mediated inflammatory and neurodegenerative conditions, while oral and ocular surface dysbiosis has been correlated with glaucoma. While developmental exposure to commensal microflora has shown to be necessary for the autoimmune and neurodegenerative responses to elevated intraocular pressure to take place, commensal bacterial products like short-chain fatty acids have regulatory effects protective against glaucoma. Summary: Alterations to human microbiotas have been associated with changes in intestinal permeability, gene regulation, immune cell differentiation, and neural functioning, which may predispose the host to glaucoma. Select microbes have been highlighted for their potential contributions to glaucoma disease progression or protection, raising the potential for microbiota-based treatment modalities. Current topical glaucoma treatments may disrupt the ocular surface microbiota, potentially having ramifications on host health. Further study of the relationships between human microbiome and glaucoma is needed.