Thyroid eye disease is an eye condition caused by abnormal thyroid hormone levels or by an autoimmune process frequently associated with autoimmune thyroid disorders.
Thyroid eye disease (TED), which is also known as Graves’ ophthalmopathy (GO) is an ophthalmologic condition primarily seen in people with autoimmune thyroid disorders. Thyroid eye disease can also occur in the absence of thyroid disease in a condition known as euthyroid Graves’ disease.
Types of Thyroid Eye Disease
There are two subtypes of thyroid eye disease:
- a more common condition related to abnormal thyroid hormone levels that resolves after abnormal thyroid hormone levels are corrected
- an autoimmune condition that runs a course independent of the thyroid disorder.
Who is Affected?
About 80 percent of all cases occur in patients with Graves’ disease. Another 10 percent of cases develop in patients with Hashimoto’s thyroiditis, and the remaining cases occur in patients without thyroid disorders although thyroid disease frequently develops later. Studies show that nearly all patients with Graves' disease will show transient signs of TED when sensitive imaging tests are used.
Signs and Symptoms
Usually, signs and symptoms are bilateral (both eyes are involved equally). Symptoms related to excess thyroid hormone levels are usually spastic and include dryness, tearing, eyelid retraction and proptosis or exophthalmos, a bulging of the eyeball. When thyroid hormone levels are too low, the primary complaint is periorbital edema, a condition of swelling affecting the entire eye and eyelid.
Autoimmune symptoms include congestion, eye muscle enlargement, inflammation, and infiltration of the orbital cavity with white blood cells and immune system chemicals. The orbital muscle may become restricted if congestion and inflammation interfere with its movement. This can cause eyelid lag, diplopia (double vision) and proptosis.
Other signs and symptoms include: erratic blinking, altered gaze, ophthalmoplegia (paralysis of eye muscle), edema, uneven pupil dilation in dim light, abnormal pigmentation of the upper eyelid, eye muscle spasm or twitching, redness, ptosis (drooping eyelid), blurriness, foreign body sensation, grittiness, strabismus, pain, staring appearance, light sensitivity (photophobia), tearing (lacrimation), visual impairment and vision loss.
Phases of Thyroid Eye Disease
- Active Phase: The active or inflammatory phase of autoimmune eye disease usually lasts from 3-6 months although it may last up to five years. During the active phase, symptoms can vary but they often worsen and are associated with an increase in TSH receptor antibodies.
- Plateau Phase: The plateau phase is characterized by decreased activity and reduced inflammation. Often, symptoms resolve during the plateau phase.
- Resolution Phase: During the resolution phase, the disease process is inactive and healing occurs. Changes that have occurred during the active phase that remain may succumb to fibrosis or scar formation although in most cases, complete healing occurs.
The Disease Course
The disease course in TED is unique to each individual. Some people have variable symptoms that wax and wane, increasing during exposures to environmental allergens and triggers. Others may have progressive symptoms, which worsen over time. In most cases, patients will experience a return to normal within 12 months.
Studies show that immune system chemicals known as cytokines and levels of TSH receptor antibodies parallel the disease course. For this reason, environmental triggers include radioiodine ablation used for hyperthyroidism may trigger or worsen symptom.
Treatment
Restoring thyroid levels to optimal levels can help resolve most symptoms of TED. In congestive eye disease, corticosteroids and other immunosuppressants are used to reduce inflammation. External beam orbital radiotherapy, used in a series of treatments, can also reduce symptoms although this treatment can cause fibrosis and cataract formation. Surgical treatments are not recommended unless vision is at risk or after the resolution phase has ended.
An avoidance of environmental triggers is important for reducing symptoms in TED and facilitating healing. Bioflavinoids, particularly flaxseed oil, and antioxidant vitamins also offer benefits for patients with TED. Lifestyle changes, including avoiding cigarette smoke are also important for healing TED.
Resource:
Elaine A. Moore, Thyroid Eye Disease, Understanding Graves’ Opthalmopathy, Sara Health Press, available at www.trafford.com, 2003.
