Graves' ophthalmopathy (also known as thyroid eye disease (TED), dysthyroid/thyroid-associated orbitopathy (TAO), Graves' orbitopathy) is an autoimmune inflammatory disorder affecting the orbit around the eye, characterized by upper eyelid retraction, lid lag, swelling, redness (erythema), conjunctivitis, and bulging eyes (exopthalmos). The autoantibodies target the fibroblasts in the eye muscles, and those fibroblasts can differentiate into fat cells (adipocytes). Fat cells and muscles expand and become inflamed. Veins become compressed, and are unable to drain fluid, causing edema.