Thyroid Eye Disease
Also known as Thyroid-Associated Ophthalmopathy or Graves’ Disease, thyroid eye disease (TED) is a form of inflammation in the tissues surrounding the eye.
The volume of the muscles controlling eye movement and the fat and connective tissues behind the eye is increased due to proliferation of cells, inflammation and the accumulation of molecules known as glycosaminoglycans (GAGs) in these tissues.
These changes along with fat production in the space behind the eye, can push the eyeball forward, leading to the characteristic appearance of the eyes (known as proptosis), and in severe cases can interfere with the function of the muscles controlling eye movement and the optic nerve.
What Are the Causes of Thyroid Eye Disease?
TED usually occurs in patients with autoimmune hyperthyroidism (overactive thyroid), but can occur with hypothyroidism (underactive thyroid).
The exact causes of TED are not well understood, but it is thought to be related to autoimmune activation of cells called fibroblasts in the orbital tissues.
TED is more frequent in women, in patients with severe hypothyroidism, and in smokers.
What Are the Symptoms of Thyroid Eye Disease?
The characteristic sign of TED is proptosis (protruding eyes) and swelling in the tissues around the eye.
Some patients notice no eye symptoms at all, some may be concerned by the appearance of their eyes only, but others can notice symptoms including irritation of the eyes, excessive tearing (often worse with exposure to cold air, wind or bright light), discomfort in or behind the eye, blurred vision or double vision. The course of TED is variable.
There is commonly an active phase lasting up to 2 years, followed by an inactive phase. In some patients it changes very little over many years, in others it may worsen or improve with time.
What Are the Treatments for Thyroid Eye Disease?
There are 3 components to treating TED
1. Treat the underlying thyroid problem
Treatment may be thyroid surgery or antithyroid medications
2. Symptomatic management
This may include use of eye shades, artificial tears (saline eye drops), lubrication drops, or sleeping with head propped up to give relief of eye symptoms.
3. Treatment with corticosteroid medication (prednisolone), radiation therapy, or surgical decompression of the eye socket.
Surgery to the eyes is only done rarely, usually in severe cases if medication or radiation therapy fails, if vision is threatened or for cosmetic correction of severe protrusion of the eyes.
Other medications such as Rituximab have also been used to treat TED. Patients should be treated according to the severity of their eye symptoms.
Mild TED is often self-limiting with symptoms improving as thyroid function returns to normal.
The mainstay of treatment is to treat the underlying thyroid problem, to quit smoking, and manage symptoms such as dry or irritated eyes with lubricating eye drops.
How Effective is Radiation Therapy for Thyroid Eye Disease?
Radiation therapy targets the inflammatory cells associated with TED. Low dose radiation therapy to the tissues behind the eye, often in combination with oral steroid medication is effective in patients with moderate to severe TED.
Radiation therapy has been found to have high response rates of between 88-95%. Studies have shown radiation therapy to be more effective than corticosteroid medication alone, but the combination of corticosteroids and radiation therapy may be better than radiation therapy alone.
The commonly used dose of radiation therapy is 20Gy in 10 fractions given 5 days a week for 2 weeks. There is some evidence that lower doses may be as effective.
What Are the Side Effects of Radiation Therapy?
Radiation therapy treatment is very well tolerated. In the short term patients may experience mild irritation of the eyes with dryness or redness.
Long term side effects include an increased risk of developing cataracts over time (12-18% rate of cataract formation).
Rare late side effects include damage to the retina or optic nerve and second cancers (although no increase in second cancers has been shown in studies with long term follow up).
The best person to discuss radiation therapy is a Radiation Oncologist. You can ask your Surgeon or General Practitioner for a referral to a Radiation Oncologist for a discussion about whether radiation therapy is a suitable treatment for you.
Find your closest radiation oncology Treatment Centre