Proptosis (exophthalmos) is an abnormal bulging of one or both eyes.
Proptosis and exophthalmos have similar meaning. Exophthalmos is usually used when referring to the eye bulging that sometimes results from thyroid disease.
Many conditions can cause proptosis. Common causes include the following:
In some types of thyroid disease, especially Graves' disease (see Thyroid Gland Disorders: Causes, the tissues in the orbit may swell, pushing the eyeball forward. This is probably the most common cause of exophthalmos.
Proptosis can develop rapidly from bleeding behind the eye (for example, after a severe injury) or from inflammation in the orbit (see Eye Socket Disorders: Inflammation of the Orbit). Tumors, either cancerous (malignant) or noncancerous (benign), can form in the orbit behind the eyeball and push it forward. An unusual noncancerous accumulation of inflammatory and fibrous tissue (pseudotumor) may cause proptosis with pain and swelling. Cavernous sinus thrombosis causes swelling because blood in the veins cannot exit the eye. Abnormal connections between the arteries and veins (arteriovenous malformations) behind the eye may cause a pulsating proptosis, in which the eye bulges forward and pulses along with the heartbeat.
The protruding eye is less protected by the eyelids, and the cornea may become too dry. As a result, infected corneal ulcers may form. Prolonged proptosis can impair vision because the optic nerve is stretched. The increased pressure within the orbit also may compress the optic nerve, which also can impair vision.
Not all people with protruding eyes have proptosis. Some people simply have prominent eyes with more white showing than normal. The extent of the protrusion can be measured with an ordinary ruler or with an instrument called an exophthalmometer. Further diagnostic tests may include computed tomography (CT), magnetic resonance imaging (MRI), or thyroid function tests.
The treatment depends on the cause. If the problem is an abnormal connection between arteries and veins, a vascular procedure may be needed to close off certain blood vessels. Thyroid disease that is severe enough to cause exophthalmos may need to be treated. However, treating the thyroid condition usually does not relieve bulging of the eyes. Treatment of bleeding or inflammation involves treating the underlying disorder (see Eye Socket Disorders: Inflammation of the Orbit). Tumors (depending on type) are treated with chemotherapy, radiation therapy, or surgery. Corticosteroids may help the inflammation caused by a pseudotumor.
Treatment that relieves the symptoms of proptosis itself includes eyeshades and eye drops if symptoms are mild or corticosteroids, radiation therapy, or surgery if the condition is more severe.
Last full review/revision September 2008 by James Garrity, MD