Forward displacement of the eyeball, making the eye appear to bulge or protrude.
Proptosis (exophthalmos) is forward displacement of the eyeball from the orbit (eye socket). It can be caused by various conditions that take up space behind or around the eye.
Key Takeaways
- Eye appears to bulge forward
- Thyroid eye disease is most common cause
- Can be measured with exophthalmometry
- Unilateral proptosis needs investigation for tumor
- May affect vision through various mechanisms
Measurement
- Exophthalmometer measures protrusion
- Normal: less than 21mm
- Difference between eyes: less than 2mm
- Asymmetry may be more significant than absolute numbers
Common Causes
Bilateral Proptosis
- Thyroid eye disease—most common
- Orbital pseudotumor (bilateral)
- Cushing syndrome
- Severe obesity
Unilateral Proptosis
- Thyroid eye disease (can be asymmetric)
- Orbital tumor
- Orbital cellulitis/abscess
- Vascular malformations
- Lacrimal gland tumors
- Metastatic cancer
Associated Problems
- Corneal exposure (drying)
- Double vision (if muscles involved)
- Vision loss (optic nerve compression)
- Cosmetic concerns
- Lid retraction appearance
Evaluation
- Measure with exophthalmometer
- Check thyroid function
- CT or MRI orbits
- Assess for optic nerve compression
- Full eye examination
When to Worry
Urgent Evaluation Needed:
- Rapid onset proptosis
- Pain with proptosis
- Vision changes
- Fever with proptosis (orbital cellulitis)
- Pulsatile proptosis (vascular cause)
Treatment
Depends on cause:
- Thyroid eye disease: medical or surgical treatment
- Tumor: surgical removal
- Infection: antibiotics
- Vascular: specialized intervention
Medical Disclaimer: This information is for educational purposes only and does not replace professional medical advice.
Medically Reviewed Content
This article meets our editorial standards
- Written by:
- Hashemi Eye Care Medical Team
- Medically reviewed by:
- Board-Certified Neuro-Ophthalmologist (MD, Neuro-Ophthalmology)
- Last reviewed:
- January 30, 2025