TED, also known as thyroid eye disease, is an autoimmune disorder caused by antibodies activating orbital fibroblasts. It is characterized by enlargement of the extraocular muscles and fatty tissue. TED occurs in approximately 50% of patients with Graves' disease, an autoimmune disorder of the thyroid gland. Diagnosis involves evaluating symptoms, signs of proptosis and extraocular muscle involvement, and laboratory/imaging tests. Management ranges from conservative measures to steroids, radiation, surgery, and the recently FDA-approved treatment teprotumumab. Complications include optic neuropathy.