Vitamin D Deficiency Is Associated with Severity of Dry Eye Symptoms and Primary Sjögren's Syndrome: A Systematic Review and Meta-Analysis.

We aimed to examine the correlations between vitamin D deficiency, severity of dry eye symptoms and primary Sjögren's syndrome (pSS) by performing a systematic review and meta-analysis. Online databases (PubMed, Cochrane Library, and Embase) were searched to identify controlled studies comparing (1) severity of dry eye symptoms between participants with and without vitamin D deficiency; and (2) serum vitamin D levels between patients with and without pSS. Eighteen studies were included. Overall, individuals with vitamin D deficiency had shorter tear breakup time (TBUT), lower Schirmer's test scores and higher ocular surface disease index (OSDI) score than those without vitamin D deficiency. Additionally, serum vitamin D levels were found to be lower in pSS than controls. Our findings highlight the importance of vitamin D deficiency in the severity of dry eye symptoms and pSS.