Foster, in Clinical Ophthalmic Oncology, 2007 Globe displacement caused by ipsilateral eyelid retraction, scarring, facial nerve paralysis or contralateral ptosis).īenson Chen. Causes include enlarged eye globe (high myopia, buphthalmos) extraocular muscle weakness or paralysis contralateral enophthalmos asymmetrical orbital size (congenital, post-irradiation, post-surgical) and asymmetrical palpebral fissures (e.g. Pseudoproptosis is either the simulation of abnormal eye prominence, or a true asymmetry that is not the result of increased orbital contents. Proptosis with displacement (non-axial) is due to extraconal disease, most commonly lacrimal tumours or a mucocoele. Tumours (such as glioma and meningioma of the optic nerve and cavernous haemangioma) may also be responsible. Thyroid exophthalmos may appear months or years after the onset of a thyroid disorder but may occasionally precede it. In this case, the protrusion is caused by inflammatory swelling of the small eye-moving muscles behind the globe. Proptosis without displacement (axial) is due to intraconal, most commonly dysthyroid, eye disease.
On scans, proptosis is defined as globe protrusion greater than 21 mm anterior to the interzygomatic line on axial scans at the level of the lens. The normal amount of ocular protrusion as measured (with an exophthalmometer) from the lateral orbital rim to the corneal apex is 14–21 mm in adults protrusion greater than 21 mm or a 2-mm change is abnormal. The term exophthalmos is sometimes used, particularly when the proptosis is related to thyroid dysfunction. Proptosis is the anterior displacement of one or both eye globes within the bony orbit.
ProfessorCrispian Scully CBE, MD, PhD, MDS, MRCS, FDSRCS, FDSRCPS, FFDRCSI, FDSRCSE, FRCPath, FMedSci, FHEA, FUCL, FBS, DSc, DChD, DMed (HC), Dr (hc), in Scully's Medical Problems in Dentistry (Seventh Edition), 2014 Proptosis
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