Bulging or protruding of one or both eyes is called proptosis or exophthalmos. Exophthalmos is usually used when describing bulging eyes caused by Graves disease, a disorder causing overactivity of the thyroid gland (hyperthyroidism Hyperthyroidism Hyperthyroidism is overactivity of the thyroid gland that leads to high levels of thyroid hormones and speeding up of vital body functions. Graves disease is the most common cause of hyperthyroidism... read more 
). Bulging eyes are not the same as prominent eyes. Some disorders that may change the appearance of the face and eyes but that do not cause true eye bulging include Cushing disease Cushing Syndrome In Cushing syndrome, the level of corticosteroids is excessive, usually due to taking corticosteroid drugs or overproduction by the adrenal glands. Cushing syndrome usually results from taking... read more 
and severe obesity.
Bulging sometimes causes other symptoms. The eyes may be dry and irritated (which causes watering) because the bulging may prevent the eyelids from closing properly. Also, people may blink less often or may appear to stare. Depending on the cause of bulging, people may have other symptoms such as double vision or difficulty focusing on objects. If bulging is prolonged, the optic nerve is stretched, which may impair vision. Vision may also be impaired if the disorder causing bulging also presses on the optic nerve.
Causes
The most common cause in adults is Graves disease Causes Hyperthyroidism is overactivity of the thyroid gland that leads to high levels of thyroid hormones and speeding up of vital body functions. Graves disease is the most common cause of hyperthyroidism... read more , which causes swelling of tissue behind and around the eye, pushing the eyeball forward. In children, the most common cause is infection.
Other causes are uncommon. They include tumors, bleeding, infections (in adults), and, rarely, inflammation of structures within the orbit without infection (called orbital pseudotumor Inflammation of the Orbit Any or all of the structures within the orbit may become inflamed because of a bodywide inflammatory disorder or an inflammatory disorder that affects only the eye. (See also Introduction to... read more ). Glaucoma that is present from birth (primary infantile glaucoma Primary Infantile Glaucoma Primary infantile glaucoma is a rare birth defect that prevents fluid from properly draining from the front part of the eye. This blockage increases pressure inside the eye, which, if left untreated... read more ) can cause the eyes to enlarge, which may seem to look similar to eyes that are pushed forward.
Evaluation
The following information can help people decide when a doctor's evaluation is needed and help them know what to expect during the evaluation.
Warning signs
In people with bulging eyes, certain symptoms and characteristics are cause for concern. They include
Loss or decrease of vision
Double vision
Eye pain or redness
Headache
Fever
Pulsation of the bulging eye
Bulging eye in a newborn or child
When to see a doctor
People with warning signs should see a doctor as soon as possible, as should those with bulging that has developed over a few days or less. People with no warning signs should see a doctor when possible, but a delay of a week or so is unlikely to be harmful.
What the doctor does
Doctors first ask questions about the person's symptoms and medical history. Doctors then do a physical examination. What they find during the history and physical examination often suggests a cause for eye bulging and the tests that may need to be done (see table Some Causes and Features of Bulging Eyes Some Causes and Features of Bulging Eyes Bulging or protruding of one or both eyes is called proptosis or exophthalmos. Exophthalmos is usually used when describing bulging eyes caused by Graves disease, a disorder causing overactivity... read more 
).
Doctors ask
How long the bulging has been present
Whether both eyes are bulging
Whether bulging seems to be getting worse
Whether the person has other eye symptoms, such as dryness, increased tear formation, double vision, loss of vision, irritation, or pain
Whether the person has symptoms of hyperthyroidism, such as inability to tolerate heat, increased sweating, involuntary shaking movements (tremors), anxiety, increased appetite, diarrhea, palpitations, and weight loss
Bulging that has developed rapidly (over a few days) suggests different causes than bulging that has developed over years. Rapid bulging in only one eye suggests bleeding in the eye socket (orbit), which can occur after surgery or injury, or infection or inflammation of the eye socket. Bulging that develops slowly suggests Graves disease Causes Hyperthyroidism is overactivity of the thyroid gland that leads to high levels of thyroid hormones and speeding up of vital body functions. Graves disease is the most common cause of hyperthyroidism... read more (when it affects both eyes) or a tumor in the eye socket (when it affects one eye).
The physical examination is focused on the eyes. Doctors examine the eyes for redness, sores, and irritation using a slit lamp What Is a Slit Lamp? A person who has eye symptoms should be checked by a doctor. However, some eye disorders cause few or no symptoms in their early stages, so the eyes should be checked regularly (every 1 to 2... read more (an instrument that enables a doctor to examine the eye under high magnification). They check whether the eyelids move as fast as the eyeball when the person looks down and check for staring. Slow eyelids and staring could indicate Graves disease.
Doctors may also check for other signs that could indicate hyperthyroidism, such as increased heart rate or blood pressure, tremors, and a swollen or tender thyroid gland in the neck.
Testing
Sometimes doctors, usually ophthalmologists, measure the degree of bulging with an instrument (exophthalmometry). Magnetic resonance imaging (MRI) or computed tomography (CT) is often done when bulging affects only one eye. Blood tests to measure how well the thyroid is working are done when Graves disease is suspected.
Treatment
When bulging leads to severe dry eyes Dry Eyes A number of other symptoms and problems can affect the eyes, including changes in the appearance of the eyes, color blindness, dry eyes, glare and halos, impaired depth perception, itchy eyes... read more , lubrication with artificial tears is needed to protect the cornea (the clear layer in front of the iris and pupil). Sometimes if lubrication is not sufficient, surgery to provide better coverage of the eye surface or to reduce bulging may be needed.
Other treatments depend on the cause of bulging. For example, antibiotics are given for infections. Bulging due to Graves disease is not affected by treatment of the thyroid condition but may lessen over time. Corticosteroids (for example, prednisone) may help control swelling due to Graves disease or orbital pseudotumor. Tumors must be surgically removed.
Key Points
Graves disease is the most common cause of bulging eyes in adults.
People with headache, fever, eye pain, or changes in vision should see a doctor quickly.
Bulging of one eye is of greater concern than bulging of both eyes.
