Thyroid Eye Disease
Thyroid disease and its effects on the eye became better known when former President George Bush and his wife, Barbara, developed disorders of the thyroid gland. The function of the thyroid gland is to secrete, or form, hormones that control a wide range of the body’s metabolic processes. Not enough hormone secretion results in hypothyroidism, which may cause fatigue, intolerance to cold, weight gain and dry skin. Too much secretion of hormone results in hyperthyroidism. Hyperthyroid persons may have heat intolerance, nervousness, weight loss and heart palpitations.
What is thyroid eye disease?
Although the thyroid gland is located in the neck, problems in the gland’s function may lead to changes in the eye and orbit (eye socket). The combination of thyroid dysfunction and eye changes is called Graves’ disease or thyroid eye disease. The eye symptoms usually appear when thyroid hormone levels are too high but can occur when these levels are normal or below n
ormal. The most obvious eye abnormality in Graves’ disease is proptosis (protrusion of the eyeballs).
Who gets Graves’ disease?
Graves’ disease if five times more likely to affect females than males. It most commonly occurs in women during their 20’s and 30’s. The disease is unpredictable in severity and duration but generally lasts months or years. In children with Graves’ disease, the eye problems tend to be less severe.
What causes thyroid eye disease?
The cause of the eye changes in Graves’ disease is unknown. However, the immune system is involved in the development of the signs and symptoms. The immune system not only fights disease but also participates in inflammation. In persons with Graves’ disease, the tissues around the eye, including the orbital fat and eye muscles, become swollen and inflamed.
What are the symptoms and signs of thyroid eye disease?
Patients with Graves’ disease may have a variety of eye symptoms that are not always recognized right away as features of a thyroid disorder:
Protrusion of one or both eyeballs.
Puffy, swollen eyelids.
Gritty, burning, irritated eyes that frequently water.
Diplopia (double vision).
Decreased vision, often following reduced brightness of colors.
Redness and swelling of the conjunctiva, the thin layer covering the white part of the eye.
Difficulty in completely closing the eyelids, especially while sleeping.
The most common eye sign in Graves’ disease is proptosis, in which the eyes appear to bulge outward. This finding is present in 70 – 90% of cases of thyroid eye disease. The swelling that causes proptosis is due to collections of fluid, fat, and inflammatory cells.
The muscles that move the eyes may also become congested and stiff. This leads to double vision, since the muscles are unable to move the eyes together. As the disease gets worse, scarring of these muscles may occur, resulting in permanent limitation of eye movements.
Proptosis may gradually increase to the extent that the cornea (the transparent tissue covering the front of the eye) becomes exposed. This exposure leads to drying and inflammation, which can progress to severe infections and ulcers of the cornea in extreme cases. Also, the orbital swelling may be so severe that the pressure within the eye increases, leading to glaucoma. The optic nerve, which is responsible for sending information received from the eye to the brain, may become strangled, resulting in severe or total visual loss.
How is thyroid eye disease diagnosed?
The characteristic eye signs often make a doctor suspicious that Graves’ disease is present. Also, blood testing frequently shows abnormal levels of thyroid hormones. Magnetic resonance imaging (MRI), computed tomography (CT) of the orbits and eyes or ocular ultrasound (sound waves) may also be used to diagnose the disease. These imaging methods can reveal swelling of the eye tissues and muscles in a pattern consistent with thyroid eye disease.
What is the treatment for thyroid eye disease?
Medical control of the thyroid disorder often does not eliminate the eye problems, which may last one or two years longer. It is not possible to predict which patients will develop advanced eye disease. Mild corneal exposure may be treated with eye drop lubricants (tear supplements) and pressure dressings to cover the eye. Some patients tape their eyes closed when they sleep to prevent further exposure. Severe cases of corneal exposure may need a lateral tarsorrhaphy, an operation that involves stitching part of the eyelids together. In some severe cases of corneal exposure, the muscles that raise the upper eyelids are surgically weakened to cause ptosis (eyelid droop) so the eyelids more adequately cover the eyes.
Infection and ulceration of the cornea may require frequent use of antibiotics to prevent perforation of the cornea.
Double vision may be corrected with the use of prisms attached to glasses, which partly compensate for limited eye movements. Surgery to reposition the eye muscles is recommended for repair of eye muscle imbalance only after Graves’ disease stabilizes.
For advanced disease with severe corneal exposure and strangulation of the optic nerve, different treatments may be used, including steroid medications, radiation and/or surgery. Steroid medication decreases the inflammation in the eye muscles and orbital tissue. Steroids usually are given orally, although the intravenous route is sometimes used. Often high doses are needed. The dosage is gradually decreased, and a low dosage is maintained until symptoms improve. Unfortunately, steroids have many possible adverse side effects.
Radiation therapy targeted to the tissue behind the eyeball is sometimes used to decrease orbital inflammation. Some physicians use combinations of radiation and steroids.
Surgical orbital decompression is an important method of relieving severe pressure on the optic nerve, which threatens vision. Various surgical procedures are used to make room in the eye socket for the swollen and thickened orbital tissue. This allows the bulging eye to relax back to its normal position.
Follow-up with an eye physician is an important part of preventive care for patients with Graves’ disease.