Exophthalmos (also called exophthalmus, exophthalmia, proptosis, or exorbitism) is a bulging of the eye anteriorly out of the orbit. Exophthalmos can be either bilateral (as is often seen in Graves' disease) or unilateral (as is often seen in an orbital tumor). Complete or partial dislocation from the orbit is also possible from trauma or swelling of surrounding tissue resulting from trauma.
In the case of Graves' disease, the displacement of the eye results from abnormal connective tissue deposition in the orbit and extraocular muscles, which can be visualized by CT or MRI.
If left untreated, exophthalmos can cause the eyelids to fail to close during sleep, leading to corneal dryness and damage. Another possible complication is a form of redness or irritation called superior limbic keratoconjunctivitis, in which the area above the cornea becomes inflamed as a result of increased friction when blinking. The process that is causing the displacement of the eye may also compress the optic nerve or ophthalmic artery, and lead to blindness.
Inflammatory/Infection:
Graves' ophthalmopathy due to Graves' disease, usually causes bilateral proptosis.
Orbital cellulitis – often with unilateral proptosis, severe redness, and moderate to severe pain, sinusitis and an elevated white blood cell count.
Dacryoadenitis
Erdheim–Chester disease
Mucormycosis
Orbital pseudotumor – presents with acute, usually unilateral proptosis with severe pain.
High-altitude cerebral edema
Granulomatosis with polyangiitis
Neoplastic:
Leukemias
Meningioma, (of sphenoid wing)
Nasopharyngeal angiofibroma
Hand–Schüller–Christian disease
Hemangioma, cavernous
Cystic:
Dermoid cyst
Vascular:
Carotid-cavernous fistula
Aortic insufficiency: manifests as a pulsatile pseudoproptosis, described by British cardiothoracic surgeon Hutan Ashrafian in 2006
Others:
Orbital fracture: apex, floor, medial wall, zygomatic
Retrobulbar hemorrhage: trauma to the orbit can lead to bleeding behind the eye.