Diabetic retinopathy (DR), the leading cause of vision loss in the working-age population, is characterized by vascular and cellular damage in the eye posterior pole due to the activation of several molecular mechanisms including the polyol, advanced end glycation (AGE) product, hexosamine, protein kinase and tissue renin–angiotensin system (RAS) pathways [46]. The gene discussed is REN; the disease is diabetic retinopathy.