Thyroid eye disease is not just about the thyroid. It is an autoimmune condition that attacks the tissues around the eye, and it can move fast when it is active. Knowing what phase you are in changes everything about how it is managed.

Thyroid eye disease (TED), also called Graves’ ophthalmopathy or thyroid-associated orbitopathy, is an autoimmune condition in which the immune system attacks the soft tissues and muscles inside the orbit, the bony socket that contains the eye. The muscles swell, the fatty tissue behind the eye expands, and the eye is pushed forward. This protrusion, called proptosis or exophthalmos, is the most visible sign of the condition but not the only one. The eyelids retract, the surface of the eye is exposed and uncomfortable, double vision can develop, and in severe cases the optic nerve is compressed at the back of the orbit. TED is most commonly associated with Graves’ disease, an autoimmune cause of an overactive thyroid, but it can occur with any thyroid status and occasionally with no thyroid disease at all.

What You Need to Know About TED

TED has two phases: an active inflammatory phase where the disease is progressing and treatment can modify it, and an inactive stable phase where inflammation has burned out but structural changes remain
The active phase typically lasts 12 to 18 months. Identifying it early allows treatment to be timed correctly
Smoking dramatically worsens TED and dramatically cuts the response to treatment. Stopping is the most important thing a patient can do
Thyroid status needs to be stable: both hyperthyroidism and hypothyroidism worsen TED
Severe sight-threatening TED with optic nerve compression requires urgent high-dose steroids or orbital decompression surgery
Most patients with mild to moderate TED improve over time with supportive care and monitoring

Smoking impact 7x Higher risk of developing TED in smokers with Graves’ disease

Active phase 12-18 mo Typical duration of the active inflammatory phase

Severe TED 3-5% Of TED cases develop sight-threatening disease

What TED Does to the Eye and Orbit

Medical illustration showing the clinical signs of thyroid eye disease including proptosis with forward protrusion of the globe, upper eyelid retraction showing sclera above the iris, periorbital swelling, and conjunctival redness — The main clinical signs of TED: proptosis, eyelid retraction, periorbital swelling, and conjunctival injection.

The immune system produces antibodies against a receptor called TSHR (thyroid stimulating hormone receptor) that is expressed both in the thyroid and in the orbital fibroblasts, the connective tissue cells inside the orbit. When these orbital fibroblasts are attacked, they produce large amounts of hyaluronic acid and differentiate into fat cells, dramatically increasing the volume of soft tissue within the rigid bony orbit. The eyeball has nowhere to go except forward. This is proptosis.

The extraocular muscles also swell and become infiltrated with inflammatory cells. They lose their elasticity. Eye movement becomes restricted and painful, and when the two eyes move at different rates, double vision results. The lower rectus muscle is most commonly affected, causing limited upward gaze, though any muscle can be involved. In severe cases, the swollen muscles at the back of the orbit compress the optic nerve as it enters the optic canal, threatening vision.

Active vs Inactive Phase

Side-by-side illustration comparing the active phase of thyroid eye disease on the left with red swollen inflamed periorbital tissues and prominent proptosis, versus the inactive stable phase on the right with settled less swollen appearance and a timeline arrow beneath — Left: active phase with inflammation and swelling. Right: inactive phase, structurally changed but settled. Treatment strategy differs completely between the two.

This is the most important concept in TED management. Everything else flows from it. The clinical activity score (CAS) is assessed at every visit, scoring signs of active inflammation: spontaneous eye pain, pain on eye movement, redness of the eyelids, conjunctival redness, chemosis, swelling of the caruncle, and increasing proptosis. A CAS of 3 or more out of 7 suggests active disease.

During the active phase, the disease is still progressing and the orbital tissues are responding to inflammation. Immunosuppressive treatments work during this window. Waiting too long to intervene means the inflammatory phase burns out with maximal structural damage that becomes fixed. During the inactive phase, rehabilitation surgery can address the residual proptosis, double vision, and eyelid changes, but it cannot reverse the orbital changes that accumulated while the disease was active.

Symptoms

TED presents differently depending on how severe and how active it is. The earliest symptoms are regularly dismissed as tiredness or allergies: grittiness, watering, light sensitivity, pressure behind the eyes. Many patients are told it’s stress. It isn’t. As the condition progresses:

Proptosis: the eye or eyes appear more prominent, the white of the eye becomes visible above and below the iris
Eyelid retraction: the upper eyelid pulls back, giving the eyes a wide, staring appearance
Periorbital swelling: puffiness of the eyelids and around the eyes, often worse in the morning
Double vision: typically on upward or sideward gaze initially, due to restricted inferior rectus
Ocular surface symptoms: dryness, grittiness, and discomfort from corneal exposure due to inadequate eyelid closure
In severe cases: reduced visual acuity, loss of color vision, or a relative afferent pupillary defect suggesting optic nerve compression

Diagnosis and Monitoring

TED is diagnosed clinically in the context of known thyroid disease, supported by thyroid function tests, TSH receptor antibody levels (TRAb), and orbital imaging. An MRI or CT of the orbits confirms proptosis, shows the degree of muscle enlargement, and crucially assesses the space between the swollen muscles at the orbital apex near the optic nerve. A tight orbital apex on imaging in a patient with visual symptoms means decompression is needed urgently. This is not a situation to watch and wait on.

Hertel exophthalmometry measures the degree of proptosis at each visit, providing an objective record of whether the condition is worsening or improving. Visual field testing and OCT of the optic nerve are performed to monitor for early signs of compressive optic neuropathy before it becomes clinically apparent.

Treatment

Selenium and supportive care for mild TED

For mild TED in the active phase, selenium supplementation (200 mcg daily for six months) has been shown in a randomised controlled trial to reduce disease activity and improve quality of life compared to placebo. It is inexpensive, well tolerated, and recommended in European guidelines for mild active TED. Alongside selenium, lubricating eye drops for surface dryness, taping the eyelids at night to protect the cornea, and prism glasses for small-angle double vision all help manage symptoms while the active phase runs its course.

Intravenous steroids for moderate-to-severe active TED

High-dose intravenous methylprednisolone is the first-line treatment for moderate-to-severe active TED. Given as weekly infusions over 12 weeks, it reduces orbital inflammation and can produce meaningful improvement in proptosis, double vision, and soft tissue signs. Response is better the earlier in the active phase treatment is started. Oral steroids are less effective and have a worse side effect profile for the same degree of immunosuppression.

Teprotumumab

Teprotumumab (Tepezza) is a monoclonal antibody that blocks the IGF-1 receptor, reducing the proliferation of orbital fibroblasts that drives the disease. It has transformed outcomes for active moderate-to-severe TED in clinical trials, producing substantial reductions in proptosis and clinical activity that exceed what was achievable with steroids alone. Currently approved in the US and increasingly available elsewhere. Given as eight intravenous infusions over 24 weeks. Side effects include hearing changes in some patients, which requires monitoring.

Orbital radiotherapy

Low-dose radiotherapy to the orbit can suppress orbital inflammation and is used in combination with steroids for moderate-to-severe active TED. Most effective for soft tissue inflammation and double vision. Not recommended in patients with diabetic retinopathy due to radiation sensitivity of already compromised retinal vessels.

Rehabilitation surgery in the inactive phase

Once TED has been inactive for at least six months, surgical rehabilitation can address the residual structural damage. The sequence matters: orbital decompression first (to reduce proptosis), then squint surgery (once the orbit is stable), then eyelid surgery (once eye alignment is corrected). Operating out of sequence leads to unpredictable results. Patients who have surgery before the active phase has fully settled risk exacerbating the disease and invalidating the surgical result.

Thyroid Control and TED: An Underappreciated Connection

Many patients assume that once the thyroid has been treated, the eye disease will follow. It doesn’t work that way. TED has its own trajectory, driven by orbital autoimmunity, and it continues to progress independently of thyroid hormone levels once established. Controlling the thyroid is necessary but not sufficient.

Radioiodine treatment for hyperthyroidism carries a specific risk: it can trigger or worsen TED, particularly in smokers or those with active or severe eye disease at the time of treatment. European guidelines recommend prophylactic steroids during radioiodine treatment for patients with any degree of TED. This is something to discuss explicitly with both the endocrinologist and ophthalmologist before radioiodine is administered.

Hypothyroidism after thyroid treatment is equally important to avoid: undertreated hypothyroidism worsens TED just as hyperthyroidism does. The target is euthyroidism, normal stable thyroid function, throughout the management of TED.

Seek Urgent Review If You Notice

Sudden reduction in vision or color vision in one or both eyes
New pain behind the eyes at rest, not just on movement
Rapid worsening of proptosis over days rather than weeks
An eye that cannot close fully, particularly at night, causing corneal exposure
Any change in the appearance of the optic nerve on OCT or visual field defect at a monitoring visit

Sight-threatening TED from optic nerve compression or severe corneal exposure is rare but moves quickly when it happens. Compressive optic neuropathy can cause permanent visual loss within days if not treated with high-dose steroids or emergency orbital decompression. Any reduction in vision in a patient with TED is an urgent ophthalmology review the same day, not a waiting list referral.

Frequently Asked Questions About Thyroid Eye Disease

My thyroid levels are normal now. Why are my eyes still getting worse?
Because the two run on separate tracks. TED and thyroid hormone levels follow separate timelines once the orbital autoimmune process has started. The orbital inflammation is driven by antibodies and immune cells that continue operating independently of what is happening in the thyroid gland itself. Getting the thyroid to normal is important, but it does not switch off the orbital disease. The eye disease runs its own course over 12 to 18 months, regardless of thyroid status.
Will my eyes ever look normal again?
Possibly. The swelling and redness of the active phase do resolve once inflammation burns out. But the structural changes that accumulate during the active phase, particularly proptosis and eyelid retraction, often persist into the inactive phase and require surgical rehabilitation to correct. How much change remains depends on how severe the active phase was and how quickly it was treated. The realistic expectation after TED is not necessarily a return to exactly how you looked before, but in most cases a significant improvement is achievable.
Do I have to stop smoking?
Bluntly: yes. Smoking is the single most modifiable risk factor for TED. Smokers with Graves’ disease have a seven times higher risk of developing significant TED than non-smokers. Smoking also reduces the response to treatment: patients who continue smoking during immunosuppressive therapy have measurably worse outcomes. If there is one thing an ophthalmologist will be categorical about in TED, it is this.
How long will I have double vision?
Double vision in TED is caused by restricted, fibrotic extraocular muscles. During the active phase it fluctuates and changes. Once the disease is inactive and stable for at least six months, squint surgery can straighten the eyes and restore single vision in most patients. Prism glasses help manage double vision while waiting for surgery. Most patients with TED-related strabismus achieve single vision in the primary position (straight ahead) after surgery, though gaze in extreme positions may remain diplopic.
What is orbital decompression and will I need it?
Orbital decompression removes one or more walls of the bony orbit to give the swollen orbital contents more space, reducing proptosis and relieving any optic nerve compression. It is needed urgently when the optic nerve is threatened, and electively in the inactive phase to reduce residual proptosis for cosmetic and functional reasons. Not everyone with TED needs it: most mild to moderate cases don’t. But for patients with significant proptosis after the active phase, decompression is often the most impactful single procedure in the rehabilitation sequence.
Can TED come back after it has settled?
Recurrence of active TED is uncommon but not impossible, particularly if thyroid status becomes unstable again or if the patient resumes smoking. The risk of recurrence is lower in patients who achieve sustained euthyroidism and remain non-smokers. Patients who have had TED should have their thyroid function monitored regularly, indefinitely. Fluctuations in thyroid status are the most common trigger for reactivation, and catching them early matters.

If you would like to learn more, the American Academy of Ophthalmology’s Graves’ disease page and the American Thyroid Association’s thyroid eye disease page offer additional patient-friendly information about the condition and its treatment.