Exophthalmos is a bulging of the eye anteriorly out of the orbit. Exophthalmos can be either bilateral (as is often seen in Grave's Disease) or unilateral (as is often seen in an orbital tumor). Measurement of the degree of exophthalmos is performed using an exophthalmometer. Complete or partial dislocation from the orbit is also possible from trauma or swelling of surrounding tissue resulting from trauma. more...
In the case of Graves Disease, the displacement of the eye is due to abnormal connective tissue deposition in the orbit and extraocular muscles (Epstein et al, 2003) which can be visualized by CT or MRI.
If left untreated, exophthalmos can causes the eye lids to fail to close during sleep leading to corneal damage. The process that is causing the displacement of the eye may also compress the optic nerve or ophthalmic artery leading to blindness.
Exophthalmos vs. proptosis
Some sources define "exophthalmos" as a protrusion of the globe greater than 18mm and "proptosis" as a protusion equal to or less than 18mm. (Epstein et al, 2003). Others define "exophthalmos" as protusion secondary to endocrine dysfunction and "proptosis" as any non-endocrine-mediated protusion .
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