Proptosis is the medical term for a protruding eyeball. Thyroid conditions and cancer are two common causes of bulging eyes. Management often involves addressing the underlying cause.

A wide range of medical conditions may lead to proptosis, but it’s most commonly seen in thyroid eye disease (TED). Infections, tumors, and injuries are some of the other potential causes of bulging eyes.

Proptosis may occur in one or both eyeballs, depending on what causes it. Bilateral proptosis is the term for two bulging eyes and unilateral proptosis for one protruding eye.

Proptosis is a bulging or protruding of one or both of your eyeballs. Generally, a diagnosis of proptosis involves an eye protrusion of more than 2 millimeters.

Proptosis is also called exophthalmos, which comes from the Greek words for “bulging eyes.”

Buphthalmos is a condition with a similar name that comes from the Greek words for “Ox-eyed.” Buphthalmos is when an eye is larger than the standard at or shortly after birth. It’s most commonly caused by congenital glaucoma.

Proptosis can be caused by a variety of reasons, but hormone-related conditions are the most common.

Thyroid eye disease (TED)

TED is an autoimmune disorder and the most common cause of proptosis in one or both eyes, as well as other eye-related challenges.

About 1 in 3 people with proptosis in one eye have excessively high thyroid hormone levels (hyperthyroidism). About 9 in 10 cases of bilateral proptosis are linked to atypical hormonal levels.

Close to 90% of people with TED have Graves’ disease, an autoimmune condition related to hyperthyroidism. It’s estimated that 1 in 4 people with Graves’ disease will develop TED.

If left untreated, TED may cause optic nerve compression that leads to permanent vision loss.

More than 90% of people with thyroid-related eye disease also experience eyelid retraction. This is where the upper or lower eyelid is drawn back.

In severe cases, eyelid retraction may not allow you to fully close your eye, which can cause eye dryness. Dry eyes increase your chance of developing ulcers or infections that may lead to vision loss.

Cancer

Proptosis in one eye can be an early symptom of primary cancers that start growing around your eyes, such as melanoma or carcinoma. Bulging eyes may also result from metastasis of cancers that first developed somewhere else.

Metastasized breast cancer is the most common cause of cancer-related proptosis, but not the only one.

A 2018 case report described a 40-year-old woman who developed proptosis and headaches as the first symptoms of a type of blood cancer called multiple myeloma.

Physical trauma

A wide range of traumatic injuries may cause proptosis. For example, an older 2013 case report described a 23-year-old football player who developed proptosis after his helmet dislodged and hit him in the right eye.

Trauma to your eye may result in a retrobulbar hematoma, which is congestion of blood deep in the tissue between your eye and skull. This buildup of blood can cause your eye to protrude.

Fracturing your skull around your eye could also potentially lead to proptosis due to air escaping your sinus and entering the area around your eye.

Infections

Severe sinus infections may lead to inflammatory conditions such as orbital cellulitis or orbital abscess. These inflammatory conditions can lead to swelling behind your eye, which puts pressure on the structure and may cause proptosis.

Blood vessel disease

A rare autoimmune disease known as granulomatosis with polyangiitis may cause abnormalities in your blood vessels, which in turn lead to proptosis and other eye complications.

Consulting a healthcare professional as soon as you notice the first signs of a bulging eye is highly advised to minimize the risk of permanent vision loss.

An eye doctor may diagnose proptosis by examining you with an exophthalmometer, a device used to measure the level of eyeball protrusion.

A healthcare professional may also review your medical history and ask you questions about any other symptoms. They’ll likely order a variety of tests to find the underlying cause of your proptosis.

Tests may include:

Imaging tests such as computed tomography (CT) scans and magnetic resonance imaging (MRI) can help the doctor:

  • search for tumor growth
  • see the extent of the inflammation in your eye
  • look for damage to your optic nerve

Treatment options for proptosis depend on the underlying cause. The first step is a comprehensive exam that allows your healthcare team to determine what’s causing a bulging eye.

General treatment options

Based on your individual needs, general management strategies for bulging eyes may include:

  • steroid injections to reduce inflammation
  • eye drops to reduce irritation and dryness
  • wearing sunglasses to help with light sensitivity
  • avoiding dust and other irritants

TED treatment

If your proptosis is related to thyroid hormones, your healthcare team will treat the underlying thyroid disease. Treatment options for hyperthyroidism may include:

Surgery

In severe cases of proptosis, orbital decompression surgery and extraocular muscle repair may be recommended to protect your vision. These surgeries increase vision in up to 82% of people.

Surgery may also help to remove tumors growing around your eye.

Cancer treatments

Along with surgery, cancers of the eye may be treated with:

Early diagnosis of proptosis is important to minimize the chances of developing complications.

In many cases, supportive treatment may be all that’s needed. About 66% of mild cases resolve within 6 months. About 95% of people with thyroid-related proptosis heal without permanent vision loss, but about 5% of people develop permanent double vision or visual impairment.

Proptosis is the medical term for bulging eyes. Thyroid conditions are the most common cause of proptosis. Other potential causes include cancer, eye injury, or infections.

It’s important to contact an eye doctor if you have proptosis. In severe cases, bulging eyes can lead to permanent vision loss. Receiving medical attention as soon as possible gives you the best possible chance of treating the underlying cause and minimizing damage to your eye.