The diagram of the bidirectional MR study of the causal associations of RA with cataract and glaucoma.

Abstract

This diagram illustrates the key assumptions that must be satisfied in the bidirectional MR study. First, the SNPs chosen as IVs should exhibit a robust association with the exposures. Second, these SNPs should be independent of confounding factors related to the exposures and outcome. Third, the selected SNPs should influence the outcome solely through the exposures, without involving other biological pathways. IVs: instrumental variables; MR: mendelian randomization; RA: rheumatoid arthritis; SNPs: single-nucleotide polymorphisms.</p