fig1

Figure 1. Flowchart of the MR study based on three core assumptions: Assumption 1 (Relevance): genetic instruments are significantly associated with the target exposure; Assumption 2 (Independence): genetic instruments are not correlated with known or potential confounders; Assumption 3 (Exclusion restriction): genetic variants influence outcomes solely through the specified exposure. Step 1 evaluates the causal effect of IRL thickness on AD, while Step 2 assesses the reverse causal effect of AD on IRL thickness. MR: Mendelian randomization; IRL: inner retinal layer; AD: Alzheimer’s disease.