EPO and diabetic retinopathy: An association was found between EPO rs551238 polymorphisms and diabetic retinopathy (allele model: OR = 0.774, 95% CI = 0.658–0.911, P = 0.002; genotype model: AC vs. CC: OR = 0.598, 95% CI = 0.402–0.890, P = 0.011; dominant model: OR = 0.561, 95% CI = 0.385–0.817, P = 0.003; recessive model: OR = 0.791, 95% CI = 0.643–0.973, P = 0.026) (Figure 4).