The impact of probiotics and prebiotics on ocular and systemic inflammation in dry eye disease: a double-masked, randomised controlled trial.

Clinical relevance: The management of dry eye disease remains a challenge due to its multifactorial nature and the involvement of chronic inflammation. Exploring the connection between gut health and eye inflammation is essential for developing more effective, holistic treatment strategies.

Background: Dry eye disease is considered to have an inflammatory component. The gut microbiome plays an important role in the regulation of low-grade chronic inflammation in different parts of the body including the eye. Probiotics and prebiotics are recognised for their beneficial effects on gut health and have been previously reported to alleviate dry eye symptoms. This study aimed to further investigate the impact of these supplements on tear and blood serum inflammatory biomarkers.

Methods: In this double-masked, randomised trial (registration number ACTRN12624000444583), 41 dry eye participants received either the probiotic and prebiotic supplements (treatment group, n = 23), or their respective placebos (control group, n = 18), for a duration of four months. The participants were followed up at one month and four months, and again one month after treatment cessation. Tear levels of inflammatory markers matrix metalloproteinase-9 (MMP-9) and tissue inhibitors of metalloproteinase-1 (TIMP-1), and serum C-reactive protein levels were determined. The MMP-9:TIMP-1 ratio also was calculated.

Results: No significant changes in MMP-9, TIMP-1, or C-reactive protein levels were observed in either group during treatment (p > 0.05). Post-treatment, MMP-9 levels rose in the treatment group (p < 0.05), and MMP-9:TIMP-1 ratios increased in both groups (p < 0.05).

Conclusions: No significant changes were found in the examined biomarkers in either group during the intervention. The apparent post-treatment rise in these markers requires further investigation, particularly in light of reported associations between MMP-9, inflammation, and ocular discomfort.