Plant-based diet quality and risk of age-related eye diseases: evidence from multi-cohorts with multi-omics insights

Plant-based diets may influence age-related eye diseases (AREDs), but whether ocular benefits depend on diet quality remains unclear. We examined associations of a healthy plant-based diet index (PDI-H) and an unhealthy plant-based diet index (PDI-U) with age-related macular degeneration (AMD), cataract, glaucoma, diabetic retinopathy (DR), and retinal vein occlusion (RVO) using the UK Biobank prospective cohort and an independent Tianjin hospital-based cross-sectional sample. Cox regression, logistic regression, propensity score matching, restricted cubic splines, subgroup analyses, multi-omics profiling, and machine learning were applied. Higher PDI-H was associated with lower risks of AMD, cataract, glaucoma, and DR, whereas higher PDI-U was associated with increased risks of AMD, cataract, and DR. Associations with RVO were weak or absent. Findings from Tianjin were directionally consistent with UK Biobank results and should be interpreted as supportive cross-sectional evidence. Proteomic and metabolomic analyses linked plant-based diet quality to inflammation, lipid metabolism, glycaemic regulation, and hormonal signalling. Predictive models incorporating dietary indices showed good discrimination for AMD and cataract, with modest but consistent AUC improvements after adding PDI-H and PDI-U to traditional risk factors. These findings suggest that plant-based diet quality, rather than plant-based eating alone, may be a modifiable determinant of major AREDs.