Proptosis and its sight-threatening mechanisms

What it is

Proptosis is the general term for any forward displacement of the eye, from any cause. Exophthalmos is narrower: it is protrusion of the eyeball due to endocrine causes, mainly thyroid eye disease, that is Graves' orbitopathy. So exophthalmos is proptosis from thyroid disease.

Exophthalmos is usually bilateral and carries lid retraction, conjunctival injection and restrictive strabismus with it. Proptosis can be unilateral or bilateral depending on the cause, and the signs that go with it depend on that cause, such as pain in orbital cellulitis and a gradual onset in tumors.

Causes and risk

Unilateral proptosis:

• Thyroid eye disease, the most common.
• Orbital cellulitis.
• Trauma.
• Tumors of the lacrimal gland and orbital tumors.

Bilateral proptosis:

• Thyroid eye disease, the most common.
• Idiopathic orbital inflammation.
• Metastatic tumors, for example neuroblastoma.

By age, Graves' disease is the most common cause in adults and orbital cellulitis the most common cause in children. Orbital or retrobulbar hemorrhage, and cavernous sinus thrombosis or fistula, are the other causes to keep in mind. Exophthalmos is most likely Graves disease.

The most common cause of proptosis is reported differently in the material. One source gives thyroid eye disease as the most common cause of both unilateral and bilateral proptosis. Another separates the two terms and gives Graves' disease as the most common cause of exophthalmos, and orbital tumors, trauma, infection and inflammation, for example orbital cellulitis and retrobulbar hemorrhage, as the most common cause of proptosis.