Serum 25-hydroxyvitamin D and tear-film stability in dry eye disease: A case-control correlation study

Dry eye disease (DED) involves tear film instability, driving symptoms and epithelial damage, with emerging evidence linking vitamin D deficiency to ocular surface inflammation. Therefore, it is of interest to compare serum 25(OH) D levels and tear parameters in 300 DED eyes (150 patients) versus 270 control eyes (135 matched subjects) at a tertiary center (2022-2024). DED patients showed severe deficiency (mean 13.79±9.36 ng/mL vs 38.13±18.76 ng/mL in controls, p<0.0001), with OSDI 39.85±10.85, TFBUT 6.38±2.75s, ST-I 9.82±5.17 mm, TMH 0.19±1.21 mm, OSS 2.71±0.21; 25(OH)D correlated positively with TMH/ST-I/TFBUT (r=0.775/0.313/0.396) and negatively with OSDI (r=-0.414), all p<0.0001. Vitamin D deficiency is strongly associated with reduced tear volume and stability, as well as worse symptoms, particularly affecting TMH and epithelial integrity. Thus, we show vitamin D as a key modifier of the tear film, supporting its role as an adjuvant therapeutic target alongside standard management.