INS and retinal disorder: Diabetes mellitus is a chronic metabolic disorder caused by defects in insulin secretion and/or insulin action, which results in hyperglycemia; prolonged hyperglycemia can lead to acute complications (e.g., diabetic ketoacidosis), chronic complications (e.g., retinopathy, chronic kidney damage, diabetic foot ulcers), and consequently, impaired quality of life (QOL) and reduced life expectancy.