INS and proliferative diabetic retinopathy: To further explore the causal relationship between DR and DN, summary-level GWAS data with non-proliferative background diabetic retinopathy and proliferative diabetic retinopathy were extracted.24 SNPs of non-proliferative background diabetic retinopathy were extracted as genetic instrumental variables.4 SNPs (rs6679677, rs9273401, rs9276710, rs17885785) were excluded with PhenoScannerV2 because these SNPs exhibited significant associations with established confounding factors (diabetes and insulin treatment).