Diabetic macular edema (DME) is a consequence of diabetic retinopathy, an eye-related complication of both Type 1 and Type 2 diabetes. Diabetic retinopathy develops when chronically high levels of blood sugar (glucose) damage and block the tiny blood vessels (capillaries) in the retina of the eye. Cut off from needed oxygen, the hypoxic retinal tissue responds by increasing, or upregulating, the expression of a small glycoprotein called vascular endothelial growth factor (VEGF). As a result of the elevated levels of VEGF, the retinal capillaries become leaky, causing the macula to swell and thicken, distorting vision. This is the condition known as DME.