TED is often difficult to diagnose and may be misdiagnosed with a range of other ophthalmic conditions, such as allergic eye disease, dry eye, myositis, and conjunctivitis. This can lead to delays in being diagnosed with TED and beginning treatment.
Diagnosis is usually based on medical history, clinical examination, blood tests, and visual assessments. Following a diagnosis of TED, disease severity is determined using a 7-point clinical activity score (CAS) that assesses pain with eye movement, redness of the eyelids, swelling of the eyelids, decreased eye movement and/or visual acuity, and the severity of bulging eyes.