Description

Dry eye disease (DED) is a multifactorial ocular surface disorder characterized by chronic tear film instability, hyperosmolarity, and ocular surface inflammation. It represents one of the most common reasons for ophthalmology consultations worldwide and has a profound impact on patient quality of life. Conventional treatment approaches primarily target symptoms and tear film supplementation, but disease-modifying interventions remain limited.

Emerging evidence suggests that the gut microbiota exerts systemic immunomodulatory effects, influencing diseases beyond the gastrointestinal tract, including ocular conditions. Dysbiosis has been implicated in autoimmune, metabolic, and inflammatory disorders, and a growing body of literature indicates that the gut-eye axis may play a role in the pathogenesis of DED. Specific microbiota-derived metabolites, microbial antigens, and immune pathways are believed to modulate ocular surface inflammation and tear film stability. This provides a strong rationale for exploring microbiome-targeted interventions in DED.

This single-arm, prospective interventional trial investigates the impact of an 8-week course of a defined dietary supplement product on gut microbiota composition and diversity, alongside established ocular surface clinical endpoints. Participants will be recruited from Istanbul Medipol University Hospital (Department of Ophthalmology) and Liv Hospitals (Vadi Istanbul and Ulus). All enrolled patients will receive the dietary supplement once daily for the study duration.

Microbiome assessment: Stool samples will be collected at baseline and at week 8, with DNA extraction followed by metagenomic sequencing. Microbiota analysis will focus on alpha diversity (e.g., Shannon index) and taxonomic/functional profiling to detect shifts in microbial composition associated with the intervention.

Ophthalmological assessment: Clinical evaluations will be performed at baseline and at week 8, including the Schirmer test, invasive tear breakup time (TBUT), Ocular Surface Disease Index (OSDI), and Dry Eye Scoring System (DESS). These standardized measures provide quantitative and qualitative assessment of tear production, stability, and patient-reported symptoms.

Safety and adherence: Safety monitoring will include the recording of adverse events throughout the trial, with particular attention to potential gastrointestinal or ocular side effects. Adherence will be assessed through participant reporting and calculation of percentage of doses taken.

Statistical considerations: Data will be analyzed using SPSS v22.0. Non-parametric tests (Mann-Whitney U for between-group and Wilcoxon signed-rank for within-group comparisons, where applicable) will be employed, as clinical data are expected to be non-normally distributed. Descriptive statistics will summarize adherence and adverse events.

This study aims to provide mechanistic insights into the gut-eye axis by linking microbiome modulation with ocular surface outcomes. Although exploratory in design, the findings may lay the groundwork for future randomized controlled trials evaluating microbiome-targeted interventions as adjunctive therapy for DED.