The Effect of Vitamins on Glaucoma: A Systematic Review and Meta-Analysis

Background: The aim of is to determine the association of vitamins with glaucoma by performing a systematic review and meta-analyses. Methods: Studies on the relation of vitamins and glaucoma published up to December 2017 were identified in the PubMed and Embase database. Data on vitamins (method of assessment), glaucoma (type and method of assessment), study characteristics and quality were recorded. In case of multiple studies for one nutrient a meta-analysis was performed. Results: A total of 629 articles were identified of which 36 were included in the systematic review. The meta-analysis included five of them (940 open-angle glaucoma (OAG) cases and 123,697 controls in total) and resulted in an odds ratio [95% confidence interval] (OR [95% CI]) of 0.58 [0.37-0.91] for dietary vitamin A, though heterogeneity was high (I-2 = 51%). After omitting studies that contributed significantly to the heterogeneity, the pooled OR [95% CI] was 0.45 [0.30-0.68] for dietary vitamin A on OAG (I-2 = 0%). For vitamin B1, C and E no significant association with OAG was found (OR [95% CI]: 0.84 [0.47-1.51]; 0.68 [0.38-1.22]; 0.95 [0.75-1.19]; respectively). However, after addressing heterogeneity, vitamin C showed a protective effect as well. Especially, foods high in these vitamins (e.g., dark green vegetables) were protective for OAG. Conclusions: Dietary intake of vitamin A and C showed a beneficial association with OAG; however, findings on blood levels of vitamins do not show a clear relation with OAG.