Thickening of the retina that takes place due to accumulation of fluid in the macula as a nonspecific response to blood-retinal barrier breakdown. Macular edema is a common pathological response to a wide variety of ocular insults, most commonly after intraocular (e.g. cataract) surgery or in association with retinal vascular (e.g. diabetic eye disease, retinal vein occlusion) or inflammatory (e.g. uveitis) disease.