Causal effect of the 25-Hydroxyvitamin D concentration on ocular diseases: A Mendelian randomization study

Observational studies report controversial associations between vitamin D levels and ocular diseases. We investigated the potential causal effect of 25-hydroxyvitamin D [25(OH)D] on ocular diseases using two-sample Mendelian randomization (MR). We examined associations between 25(OH)D and various ocular diseases including age-related macular degeneration, cataracts, diabetic retinopathy, myopia, glaucoma, conjunctivitis, keratitis and optic neuritis. Data were from genome-wide association studies of 25(OH)D and ocular diseases. We performed MR analyses using inverse-variance weighted methods with sensitivity analyses. We found no significant causal relationships between 25(OH)D and ocular diseases (all P > 0.05). Tests for heterogeneity (P > 0.05) and pleiotropy (P > 0.05) supported the MR validity. Our MR analysis does not provide evidence supporting a causal relationship between 25(OH)D and ocular disease risk in Europeans. This suggests that previous epidemiological associations may stem from shared biological factors or confounders rather than direct causality. However, further research is needed to fully elucidate the complex relationships between vitamin D and ocular health.