Exophthalmos

Proptosis is also a term sometimes used to describe a bulging eyeball or eyeballs.

Depending on what is causing bulging eyes, you may also have other associated symptoms.

For example, if exophthalmos is caused by a thyroid-related condition, such as Graves' disease, as well as bulging, your eyes may also be:

• inflamed, red and painful
• dry and 'gritty'
• tearful
• sensitive to light (photophobia)

Your vision may also be affected – for example, you may have double vision or some loss of vision.

What causes expohthalmos?

Exophthalmos can be caused by many different conditions. It is important that the underlying cause is identified so appropriate treatment can be given.

Conditions that affect the thyroid gland are a common cause of exophthalmos. The thyroid is a small gland at the base of the throat that controls your metabolism (the rate at which your body uses energy).

A thyroid condition that affects the eyes is known as thyroid eye disease or thyroid orbitopathy.

An overactive thyroid gland can sometimes lead to a thyroid eye disease and symptoms such as puffy, swollen eyes, tearing and bulging eyeballs.

Exophthalmos is sometimes related to tumours that develop in the eyes. For example, a capillary haemangioma is a type of tumour that can develop in the eye cavity during childhood. It can sometimes cause exophthalmos.

A pleomorphic lacrimal gland adenoma is a painless, slow-growing eye tumour that can develop in adults in their 50s. In some cases, it can also cause exophthalmos.

Diagnosing exophthalmos

Exophthalmos is often easy to recognise from the appearance of the eyeballs, which clearly bulge or protrude from the sockets, exposing most of the whites of the eyes.

How much the eyeball bulges, the direction it protrudes and other associated symptoms will often provide clues about the underlying cause. However, further tests will be needed to confirm a diagnosis.

Your GP may refer you to an ophthalmologist (a specialist in diagnosing and treating eye conditions). The ophthalmologist will check how well you are able to move your eyes. They may also use an instrument called an exophthalmometer to measure how far your eyeball protrudes.

If the ophthalmologist wants to examine your eye socket in more detail, a scan such as a computerised tomography (CT) scan or magnetic resonance imaging (MRI) scan may be used.

You may also have a blood test or a thyroid function test to check your thyroid gland is working properly.

Treating exophthalmos

Treatment for exophthalmos will depend on the underlying cause.

If a thyroid problem is causing your eyes to bulge, treatment to stop your thyroid gland producing excess amounts of thyroid hormones may be recommended.

This can be achieved using medication, such as thionamides, or by having radioiodine treatment, where a chemical called radioactive iodine is swallowed, which shrinks your thyroid gland.

The use of corticosteroids (medication that contains manmade versions of the hormone cortisol) can help reduce painful eye inflammation.

If your eyes are dry, sore and inflamed, a lubricant, such as artificial tears, may also be prescribed to moisten your eyes and relieve irritation.

In cases where exophthalmos is caused by a tumour, treatments such as radiotherapy, chemotherapy or surgery may be appropriate. A combination of these treatments may sometimes be recommended.

Read more about treating exophthalmos.

Complications

In very severe cases of exophthalmos, you may not be able to close your eyes properly. This can damage your cornea (the transparent tissue that covers the front of your eyeball) by causing it to dry out.

If your cornea becomes very dry, an infection or ulcers (open sores) may develop. If left untreated, these could damage your vision.

Other possible complications of exophthalmos include conjunctivitis (inflammation of the lining of the eye) and optic atrophy (deterioration of the optic nerve).

Outlook

As long as the underlying cause of exophthalmos is identified at an early stage, it can usually be successfully treated.

After treatment, any pain, redness, swelling or irritability will usually settle down after a few months, although in some cases it may take longer.

If exophthalmos is caused by thyroid eye disease, your eyes may not go back to normal. In up to one in 20 people, thyroid eye disease may get worse, resulting in double vision or some degree of visual impairment.