The Efficacy of Oral Vitamin Supplementation in Dry Eye Disease: A Systematic Review

INTRODUCTION: Vitamins are micronutrients with a wide range of anti-inflammatory, immunomodulatory, regulatory and antioxidant properties. Several studies have shown that vitamins play a crucial role in the homoeostasis of the ocular surface. Deficiency of certain vitamins might be associated with the severity and incidence of dry eye disease. METHOD: This paper reviewed the current evidence on the effect of oral vitamin supplementation on signs and symptoms of dry eye disease. The literature review was conducted in five English archive databases (Pubmed, Cochrane, Embase Ovid, Web of Science and Scopus) from April 2024 to January 2025, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (Prospero CRD42024629589). Eligibility criteria included studies that reported the Schirmer test, tear film break-up time, corneal fluorescein staining scores, lid hyperaemia, the ocular surface disease index and visual analogue pain scale. RESULTS: A total of 13 eligible studies, which included vitamins A, B1, B12 and D, were assessed by two independent reviewers for quality and data extraction. Of these, most investigated the efficacy of vitamin D (61.5%), vitamin A (23%) and a mix of vitamin B1 and mecobalamin (15.5%). No studies reported on the efficacy of vitamin C supplementation, and none were judged to be of high quality. CONCLUSION: The available evidence is limited due to not being well-controlled or adequately powered, having a very short follow-up duration and variable dosage of supplementation.