Effect of a Dietary Supplement on Gut Microbiota and Ocular Surface Outcomes in Dry Eye Disease

Inclusion Criteria: Adults aged 18-65 years. Clinical diagnosis of dry eye disease with clinically significant symptoms, defined as Ocular Surface Disease Index (OSDI) score ≥23 at screening and/or baseline. Evidence of tear film instability consistent with dry eye disease, defined as fluorescein tear break-up time (TBUT) ≤10 seconds in at least one eye at screening and/or baseline. Willing and able to provide written informed consent. Willing to maintain habitual diet and lifestyle during the study period and to avoid initiating new microbiome-active products (e.g., probiotic/prebiotic/synbiotic supplements) during the intervention. Exclusion Criteria: Current restrictive dietary pattern likely to materially alter gut microbiota (e.g., ketogenic diet, elimination diets, prolonged fasting) or planned major dietary change during the study period. Colonoscopy within the past 4 weeks. Systemic antibiotic use within the past 4 weeks. Use of probiotic, prebiotic, synbiotic, postbiotic, or fecal microbiota-related products within the past 4 weeks. Active ocular infection or acute ocular inflammation requiring treatment escalation (e.g., acute blepharitis flare, active allergic conjunctivitis requiring escalation), at screening/baseline. Sjögren syndrome or other active systemic autoimmune disease with clinically significant ocular involvement, in the investigator's judgment. Ocular surgery (including refractive surgery) or significant ocular trauma within the past 6 mo…