Investigation of the Association between the Oral and the Gut Microbiome inGlaucoma

Objective: Glaucoma is characterized by a progressive degeneration of retinal ganglion cells (RGC) and their axons leading to painless damage of the visual field and finally blindness. The exact pathophysiology of RGC loss remains unknown. Alterations in the microbiome may be linked to neurodegenerative conditions such as Alzheimer’s and Parkinson’s diseases, possibly due to associated chronic low-grade inflammation. A recent study linked alterations in the oral microbiome and glaucoma. Methods: We investigated the microbiome of salivary and fecal samples in patients with normal tension glaucoma (10), ocular hypertension (11) and controls (11) using a case-control design with 16S rDNA sequencing. Results: For controls, but not the patient groups, salivary and fecal microbiome diversity was correlated in a given patient, suggesting an uncoupled saliva and fecal microbiome in the diseased groups. Such findings suggest that normal tension glaucoma (NTG) and ocular hypertension (OHT) might have similar characteristics. However, ocular hypertension patients seem to be resistant to neurodegenerative disease progression indicating that the uncoupled microbiome might affect characteristics linking ocular hypertension and normal tension glaucoma together. Moreover, we found the salivary microbiome to contain more differential taxa-level abundances of microorganisms suggesting the salivary microbiome might be advantageous to use in future studies investigating novel biomarkers in ophthalmic neurodegenerative diseases. Conclusion: The finding of an uncoupled microbiome might indicate comparable characteristics among glaucoma patients and ocular hypertension patients.