Thyroid Eye Disease: Activity, Severity and Treatment

Last updated: October 2026

Thyroid eye disease (TED, also called Graves orbitopathy or thyroid-associated orbitopathy) is the most common cause of proptosis in adults, unilateral or bilateral. The key skills are deciding whether the disease is active, how severe it is, and spotting the sight-threatening complications early.

Essentials

• An autoimmune disease in which orbital fibroblasts (driven by TSH-receptor and IGF-1 receptor signalling) cause swelling of the extraocular muscles and orbital fat.
• Most patients have Graves hyperthyroidism, but TED can occur in euthyroid or hypothyroid patients.
• Smoking is the strongest modifiable risk factor. It worsens disease and reduces treatment response; help every patient stop.
• Radioactive iodine can trigger or worsen TED, particularly in smokers or active disease. Steroid cover is often given.
• The disease follows Rundle's curve: an active inflammatory phase lasting months to a couple of years, then a stable inactive phase. Medical treatment works in the active phase; rehabilitative surgery is done in the inactive phase.

Signs to know by name

• Upper lid retraction (Dalrymple sign): the most common sign
• Lid lag on downgaze (von Graefe sign)
• Proptosis: measure with an exophthalmometer, and use the same instrument each time
• Restrictive strabismus: the inferior rectus is most commonly involved, then the medial rectus, so elevation and abduction are typically limited. Remember the order with "I'M SLOw" (inferior, medial, superior, lateral, obliques).
• Raised IOP on upgaze from a tight inferior rectus; measure IOP in primary position
• Superior limbic keratoconjunctivitis, exposure keratopathy, and lagophthalmos

Is it active? Clinical Activity Score (CAS)

Score one point for each feature present. A score of 3 or more out of 7 indicates active disease.

1. Spontaneous retrobulbar pain
2. Pain on attempted eye movements
3. Redness of the eyelids
4. Redness of the conjunctiva
5. Swelling of the eyelids
6. Inflammation of the caruncle or plica
7. Conjunctival oedema (chemosis)

At follow-up, a further 3 points (on the 10-point version) assess an increase in proptosis, a fall in eye movements, and reduced vision.

How severe is it? (EUGOGO)

Dysthyroid optic neuropathy: don't miss it

• Caused by compression of the optic nerve at the orbital apex by enlarged muscles ("apical crowding"). It can occur without much proptosis.
• Check visual acuity, colour vision, pupils (RAPD), visual fields and the disc at every visit.
• Treat urgently with high-dose IV methylprednisolone. If there is no adequate response within about 1–2 weeks, proceed to urgent orbital decompression.

Treatment options for active moderate-to-severe disease

• IV methylprednisolone: a commonly used EUGOGO regimen gives a cumulative dose of 4.5 g over 12 weeks. Keep the total cumulative dose below 8 g, and check liver function, blood pressure and blood sugar.
• Mycophenolate added to IV steroids improves response.
• Teprotumumab (IGF-1 receptor blocker) reduces proptosis and diplopia. Side effects include hearing problems, hyperglycaemia and muscle cramps; it is expensive and not widely available.
• Other options in selected patients: tocilizumab, orbital radiotherapy (especially for motility problems), and rituximab.

Rehabilitative surgery: the order matters

Once the disease has been inactive for several months, surgery is done in this sequence, because each step affects the next:

1. Orbital decompression (for proptosis or exposure)
2. Strabismus surgery (for diplopia; usually recessions of tight muscles)
3. Eyelid surgery (for lid retraction and cosmesis)

Imaging pearl

On CT or MRI, TED enlarges the muscle belly while sparing the tendon ("Coca-Cola bottle" sign). Orbital myositis typically involves the tendon too. Look for apical crowding in suspected optic neuropathy.

Related: oculoplasty notes and cranial nerve palsies (for other causes of diplopia).