- 1.
What is proptosis?
Proptosis is a forward protrusion of one or both eyeballs. Unilateral proptosis is frequently defined as asymmetric protrusion of one eye by at least 2 mm. Normal upper limits for proptosis are approximately 22 mm in Caucasians and 24 mm in African Americans.
- 2.
How is proptosis diagnosed?
Clinically, proptosis can be recognized best by observing the globes from above, over the patient’s forehead, or from below with the head tilted back. It is measured with an exophthalmometer based at the lateral orbital rim. The amount of proptosis can also be quantified by measuring globe protrusion on a computed tomographic (CT) scan ( Fig. 34-1 ).
Figure 34-1
Computed tomographic scan demonstrating proptosis of the right globe secondary to thyroid-related enlargement of the rectus muscles.
- 3.
List common problems associated with proptosis.
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Exposure keratopathy frequently develops secondary to a poor blink mechanism over the protruding globe. Patients can have mild symptoms of irritation and foreign body sensation, or they may experience more severe symptoms associated with corneal abrasions and ulcers ( Fig. 34-2 ).
Figure 34-2
Severe conjunctival chemosis with corneal erosion secondary to proptosis caused by an orbital lymphoma.
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Diplopia (double vision) can result from unilateral or bilateral proptosis with displacement of the globes or poor extraocular muscle function.
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Optic nerve compression can occur with space-occupying lesions of the orbit, which cause proptosis. Indications of nerve compression include decreased visual acuity, relative afferent pupillary defect, color vision deficit, and visual field defect of the affected eye. This is a medical emergency and requires prompt therapeutic intervention, surgically or medically.
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- 4.
What is the most common cause of unilateral proptosis?
Thyroid eye disease (Graves’ ophthalmopathy).
- 5.
What is the most common cause of bilateral proptosis?
Thyroid eye disease.
- 6.
What are other causes of proptosis?
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Idiopathic orbital inflammatory disease (orbital pseudotumor)
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Orbital infectious cellulitis
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Orbital tumors (benign or malignant)
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Lacrimal gland tumors
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Trauma (retrobulbar hemorrhage)
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Orbital vasculitis (i.e., polyarteritis nodosa, Wegener’s granulomatosis)
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Mucormycosis
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Carotid–cavernous fistula
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Orbital varix
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- 7.
List the causes of pseudoproptosis.
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Unilateral high axial myopia can mimic proptosis, owing to the increased length of the myopic eye.
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Actual enophthalmos of one eye may cause apparent proptosis of the contralateral eye ( Fig. 34-3 ).
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