The Ocular and Gut Microbiome Axis in Understanding Glaucoma: A Systematic Review

Area of Science:

• Ophthalmology
• Microbiology
• Genetics

Background:

• Glaucoma is a leading cause of irreversible blindness, characterized by retinal ganglion cell loss.
• Elevated intraocular pressure (IOP) is a primary risk factor, but microbiota's role is increasingly recognized.
• Ocular and gut microbiota may influence glaucoma onset and progression.

Purpose of the Study:

• To characterize ocular and gut microbiota in patients with various glaucoma types.
• To investigate the relationship between microbiota composition and glaucoma.
• To explore potential links between dysbiosis, dry eye disease, and glaucoma.

Main Methods:

• Systematic literature review following PRISMA 2020 guidelines.
• Searches conducted between June-September 2025, identifying 14 relevant articles from 121.
• Analysis of ocular and gut microbiota alterations in glaucoma patients versus controls.

Main Results:

• Glaucoma is associated with Mendelian genetic predisposition influencing microbiota.
• Benzalkonium chloride (BAK) treatment increased Gram-negative bacteria and lipopolysaccharide synthesis.
• Glaucoma patients showed reduced Corynebacterium mastiditis and Actinobacteria, with increased Firmicutes, Proteobacteria, and Verrucomicrobiota.
• Dysbiosis was more severe in glaucoma patients with dry eye disease.

Conclusions:

• Significant ocular and gut microbiota differences exist between glaucoma subtypes and controls.
• Age-related dysbiosis and epigenetic factors contribute to glaucoma development.
• Microbiota profiling presents potential for improved glaucoma prediction, management, and treatment.