APOA1 and age-related macular degeneration: When examining the effects of specific metabolites, heterogeneity was detected for the effects of apolipoprotein A1 levels on early AMD (IVW: p = 2.72 × 10−6; MR-Egger: p = 6.50 × 10−6), and horizontal pleiotropy was detected for the effects of alanine levels on early AMD (p = 0.043) (Table 1).