Type 2 diabetes mellitus (T2DM) is the most common metabolic and multifactorial disease in which both genetic and environmental factors are involved. In diabetes, the defects in the cellular metabolism result in higher levels of free radicals. These radicals react with other vital cellular molecules, which are responsible in diabetes side effects and known as diabetic retinopathy (DR), a disease of the retina that results in impairment or loss of vision. In the present study, we investigated the expression of glutathione S-transferases class theta 1 (GSTT1) in type 2 DR subjects. Highly significant differences (P ≤ 0.05) were observed in GSST1 expression in DR patients compared with diabetic and control groups.