Therefore, we performed a comparative, self-controlled, and blinded study evaluating, as a primary endpoint, retinal microvascular changes (vasculature perfusion and density) by optical coherence tomography angiography (OCTA) before, during, and after controlled insulin-induced hypoglycemia in type 1 or 2 diabetes mellitus (DM) patients with or without DR and controls. The gene discussed is INS; the disease is diabetes mellitus.