For this, in accordance with the available resources, we selected five polymorphisms (−2549 I/D in the VEGF gene, −429 T/C and −374 T/A in the RAGE gene, rs7903146 in the TCF7L2 gene, BglII in the ITGA2 gene) and conducted a case–control study comparing allele and genotype frequencies in three groups: DR patients, T2DM patients without DR, and healthy controls. The gene discussed is TCF7L2; the disease is type 2 diabetes mellitus.