Diabetic macular edema (DME), affecting approximately 5.5–7% of all patients with diabetes, is one of the most common causes of severe visual impairment and blindness in people of working age [1–3].Treatment with intravitreal injections of anti-vascular endothelial growth factors (anti-VEGF) is established as first-line therapy for DME that can maintain or even improve visual acuity [3].Successful management of this chronic disease requires consistent long-term treatment and hence high patient adherence [4], which is positively associated with patients’ health literacy [5]. This evidence concerns the gene VEGFA and diabetes mellitus.