Macular edema is a complication of nonproliferative retinopathy in which the capillary walls may lose their ability to control the passage of substances between the blood and the retina. Fluid can leak into the part of the eye where focusing occurs, the macula. When the macula swells with fluid -- a condition called macular edema -- vision blurs and can be lost entirely. Although nonproliferative retinopathy usually does not require treatment, macular edema must be treated. Fortunately, treatment is usually effective at stopping and sometimes reversing vision loss.