A Slovenian study published in 2012 found that the GSTT1 null genotype was associated with an increased risk of diabetic retinopathy (DR) in T2DM (OR = 2.303, 95% CI = 1.649–3.216, p < 0.001) while the GSTM1 null genotype conferred a reduced risk of T2DM DR (OR = 0.475, 95% CI = 0.339–0.668, p < 0.001). This evidence concerns the gene GSTM1 and type 2 diabetes mellitus.