Thyroid Eye Disease

What is thyroid eye disease

Thyroid eye disease often occurs in people who develop an overactive thyroid gland. Swelling of the muscles and other tissues in the orbits causes the eyes to become pushed forward and more prominent. The eyes often take on a more staring appearance. In more severe cases the swelling may cause stiffness of the muscles which move the eyes. This can cause a "squint" to develop and may result in double vision. Occasionally the swelling behind the eyeball may press on the nerve from the eye to the brain and distrupt vision. Thyroid eye disease is also called thyroid opthalmopathy, Graves eye disease or dysthyroid eye disease.

What causes thyroid eye disease

Most people with thyroid eye disease have or had or will subsequently develop an overactive thyroid gland. In 20% the thyroid eye disease develops in people who do not have an overactive thyroid at the time (may subsequently develop this years later). In 40% thyroid eye disease occurs whilst the thyroid is overactive and in 40% can occur years after the overactive thyroid has been treated successfully.

Overactivity of the thyroid gland is usually caused by an "autoimmune condition" This means that cells which normally protect the body from infection develop a "fault" and begin to recognise the thyroid gland as foreign material and attack it. This stimulates the thyroid gland to produce extra thyroid hormones. The attacking process may spill over to the cells behind the eye causing them to swell. It is not yet known why cells develop the fault that causes them to attack the thyroid gland or why only some patients with overactivity of the thyroid develop thyroid eye disease. Thyroid eye disease does appear to be more common in smokers.

Does everyone with an overactive thyroid develop thyroid eye disease No. Severe thyroid eye disease occurs in possibly only 2% with an overactive thyoid. Smoking increases the risk nearly 8 fold. The risk is worse in males, older women and in those with severe overactive thyroid conditions. Mild thyroid eye disease can occur in many more and your specialist will check for this.

Are there any other symptoms

The commonest symptoms are mild soreness and grittiness of the eyes. Surprisingly one eye is may be more affected than the other. The eyes may become watery uncomfortable and sensitive to light. There may be some puffiness of the upper eyelid or around the eyes. This is often worse in the morning.

What can be done to prevent thyroid eye disease

Giving up smoking and careful checks of the thyroid blood level may help to prevent eye problems getting worse but despite this other treatment is sometimes required.

Is it important to treat the overactive thyroid condition

Yes, this is vital for as long as the thyroid remains overactive, the thyroid eye disease is not likely to settle. Thyroid eye disease ironically can be made worse during the actual treatment of the overactive thyroid and so certain preventative measures are taken to reduce this risk. If radioactive iodine therapy is used then you will be asked to take prednisolone (a steroid) for 3 months after therapy. The specialist will also check your thyoid function regularly so that thyroid replacement hormone medicine can begin as soon as possible to prevent the development of an underactive thyroid brought on by the radioactive iodine.An underactive thyroid might worsen the thyoid eye condition if left unchecked hence the reason for early detection and treatment.

The specialist will also aim to keep your blood TSH level suppressed at all times as a rise might again worsen your eye condition. Medical therapy e.g. carbimazole or thyoidectomy can also worsen the eye condition at the outset if the thyoid is very overactive and so once again precautions will be taken to minimise the risk. Thyroid hormone replacement will be prescribed early on to prevent hypothyoidism worsening the eyes.