Bulging Eye (Proptosis)

Proptosis (prop-TOE-sis), also called exophthalmos, is forward displacement of the eyeball, making the eye appear to bulge. It can affect one eye (unilateral) or both (bilateral) and has many potential causes, most commonly thyroid eye disease.

What Proptosis Looks Like

Signs of proptosis include:

• Eye appearing more prominent or "staring"
• Visible white of eye (sclera) above or below iris
• Eyelids not fully closing (lagophthalmos)
• One eye appearing larger than the other
• Difficulty fully closing eyes during sleep
• Sensation of pressure behind the eye
• May have redness, swelling of eyelids

Causes of Proptosis

Bilateral (Both Eyes)

Thyroid eye disease (Graves' orbitopathy)

• Most common cause of bilateral proptosis
• Associated with hyperthyroidism (Graves' disease)
• Can occur with normal thyroid function too
• May have eyelid retraction, double vision
• Swelling of eye muscles and fat

Unilateral (One Eye)

Requires workup to determine cause:

Inflammatory

• Orbital pseudotumor (idiopathic orbital inflammation)
• Thyroid eye disease (can be asymmetric)
• Sarcoidosis, granulomatosis with polyangiitis

Tumors

• Cavernous hemangioma (benign)
• Lymphoma
• Lacrimal gland tumors
• Meningioma
• Metastatic cancer

Vascular

• Carotid-cavernous fistula (pulsatile proptosis)
• Orbital varix (changes with position/straining)
• Arteriovenous malformation

Infection

• Orbital cellulitis—painful, red, swollen, urgent

Structural

• Shallow orbits (congenital)
• High myopia (eye naturally longer)

Rapid Onset—Emergency

Orbital cellulitis

• Pain, redness, swelling
• Fever
• Limited eye movement
• Can spread to brain—emergency

Warning Signs

Complications of Proptosis

Exposure Problems

When the eye protrudes, lids may not protect it:

• Dry eye—surface exposed, not well lubricated
• Corneal damage—exposure keratopathy
• Infection risk—inadequate protection
• Cosmetic concerns

Vision Threat

• Optic nerve compression—enlarged muscles can compress nerve
• Corneal ulceration—from exposure
• Double vision—from muscle involvement

How Proptosis Is Evaluated

Clinical Examination

• Exophthalmometry—measuring how far eye protrudes
• Comparison between eyes
• Eyelid position assessment
• Eye movement testing
• Vision and pupil examination
• Checking for pulsation or bruit (abnormal sound)

Imaging

• CT orbits—shows bone and soft tissue well
• MRI orbits—better soft tissue detail
• Helps identify tumors, inflammation, vascular lesions

Blood Tests

• Thyroid function—TSH, free T4
• Thyroid antibodies—TSI, TPO antibodies
• Inflammatory markers—if infection suspected

Treatment Options

Treatment depends on the cause:

For Thyroid Eye Disease

Active/inflammatory phase:

• Smoking cessation—critical; smoking worsens disease
• Selenium supplements—may help mild cases
• Steroids—for moderate-severe inflammation
• Teprotumumab (Tepezza)—FDA-approved biologic

Stable/chronic phase:

• Orbital decompression surgery—removes bone to create room
• Strabismus surgery—for double vision
• Eyelid surgery—for retraction

For Inflammatory Conditions

• Steroids
• Steroid-sparing immunosuppressants
• Treatment of underlying condition

For Tumors

• Surgical removal when indicated
• May need radiation
• Depends on tumor type

For Infection (Orbital Cellulitis)

• IV antibiotics—urgent
• Surgical drainage—if abscess present
• Hospitalization—usually required

Supportive Care

• Lubricating drops and ointment—protect exposed surface
• Taping eyelids at night—if incomplete closure
• Moisture chambers—special goggles
• Elevating head of bed—may reduce swelling

Frequently Asked Questions

Can thyroid eye disease occur with normal thyroid levels?

Yes. About 10% of people with thyroid eye disease have normal thyroid function (euthyroid). Thyroid antibodies may still be present.

Will my proptosis go away?

It depends on the cause. Inflammatory proptosis may improve with treatment. Thyroid eye disease typically improves but some proptosis may persist, sometimes needing surgery. Tumor-related proptosis requires treatment of the tumor.

Is proptosis the same as "bug eyes"?

"Bug eyes" is a colloquial term often referring to prominent eyes, which can be due to proptosis (forward displacement) or lid retraction (eyelids pulled back) or both. Thyroid eye disease commonly causes both.

Can I go blind from proptosis?

Vision loss can occur if the optic nerve is compressed or if the cornea is severely damaged from exposure. This is why evaluation and treatment are important. Most people maintain good vision with appropriate care.

Does everyone with Graves' disease get proptosis?

No. About 25-50% of people with Graves' disease develop eye involvement (thyroid eye disease). Not everyone with thyroid eye disease develops significant proptosis.

References