Bibliography

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).

3.List common problems associated with proptosis.

•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).

•Diplopia (double vision) can result from unilateral or bilateral proptosis with displacement of the globes or poor extraocular muscle function.

•Optic nerve compression can occur with space-occupying lesions of the orbit, which cause prop­ tosis. 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.

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?

•Idiopathic orbital inflammatory disease (orbital pseudotumor)

•Orbital infectious cellulitis

•Orbital tumors (benign or malignant)

•Lacrimal gland tumors

•Trauma (retrobulbar hemorrhage)

•Orbital vasculitis (i.e., polyarteritis nodosa, Wegener’s granulomatosis)

•Mucormycosis

•Carotid–cavernous fistula

•Orbital varix

7.List the causes of pseudoproptosis.

•Unilateral high axial myopia can mimic proptosis, owing to the increased length of the myopic eye.

•Actual enophthalmos of one eye may cause apparent proptosis of the contralateral eye (Fig. 34-3).

•Upper eyelid retraction produces a more prominent-appearing eye. This often coexists in cases of thyroid ophthalmopathy.

8.Which neuroimaging test is best to evaluate the etiology of proptosis?

CT scans are superior in most cases of proptosis, because the relationship of the orbital process to the orbital bones is better visualized. Magnetic resonance imaging (MRI) may be desirable in certain cases when optic nerve dysfunction is present. Plain films are not used for diagnostic accuracy in cases of proptosis.

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CHAPTER 34  PROPTOSIS  279

Figure 34-1.  Computed tomographic scan demonstrating proptosis of the right globe secondary to thyroid-related enlargement of the rectus muscles.

Figure 34-2.  Severe conjunctival chemosis with corneal erosion secondary to proptosis caused by an orbital lymphoma.

Figure 34-3.  Patient with enophthalmos of the left eye secondary to old trauma, which is causing apparent proptosis of the right eye.

9.What clinical entity is frequently associated with unilateral or bilateral painless proptosis, eyelid retraction, eyelid lag on downward gaze, and motility disturbances?

Thyroid ophthalmopathy associated with Graves’ disease (Fig. 34-4) is a complex, multisystem, autoimmune disorder. Patients can be hyperthyroid, hypothyroid, or euthyroid when manifesting ophthalmic symptoms. Eye problems develop as a result of inflammation and enlargement of various extraocular muscles (most frequently the inferior rectus and medial rectus) and peribulbar tissues. CT scan or MRI results often show fusiform enlargement of the involved extraocular muscles with sparing of the tendon that attaches the muscle to the globe. Proptosis and eyelid retraction cause corneal problems, and muscle enlargement in the orbit causes diplopia and possibly optic nerve compression. Treatment is in stages, depending on the severity of the eye disease. Systemic and laboratory evaluation is mandatory.

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Figure 34-4.  Proptosis and eyelid retraction caused by thyroid ophthalmopathy.

KEY POINTS: CLINICAL SIGNS OF GRAVES’ DISEASE

1. Unilateral or bilateral proptosis

2. Eyelid retraction with lateral flare

3.Lagophthalmos

4.Diplopia

5.Pretibial myxedema

10.What clinical entity is frequently associated with unilateral proptosis, pain, conjunctival injection, and motility disturbances in an adult?

Orbital inflammatory pseudotumor is a nonspecific idiopathic inflammatory disease of the orbit. Inflammation may be localized to a muscle, the lacrimal gland, or sclera or may be diffuse. Other possible signs include eyelid erythema or edema, palpable mass, decreased vision, uveitis, hyperopic shift, and optic nerve edema. Bilateral disease is more common in children. CT scan results may show thickening of one or more extraocular muscles (including the tendons), lacrimal gland enlargement, or thickening of the posterior sclera. Treatment is primarily with corticosteroids and possibly radiation therapy.

11.What clinical entity is characterized by unilateral proptosis, pain, fever, decreased ocular motility, erythema, and edema of the eyelids?

Infectious orbital cellulitis involves an infection (usually bacterial) that has extended posterior to the orbital septum. Once past the orbital septum barrier, infection can spread rapidly and cause serious complications such as meningitis or cavernous sinus thrombosis. The most common organisms include staphylococci, streptococci, anaerobes, and Haemophilus influenzae (in children younger than 5 years of age). The most common source of infectious spread to the orbit is an ethmoid sinusitis. Treatment is with intravenous antibiotics.

12.What should be done for persistent proptosis or progression of infection despite adequate antibiotic treatment in a case of orbital cellulitis?

The situation is highly suggestive of an orbital subperiosteal abscess. CT scanning should be performed to confirm this diagnosis and locate the abscess. Definitive treatment consists of surgical drainage and continued intravenous antibiotics.

13.What clinical entity is characterized by a child younger than 6 years of age with gradual, painless, progressive, unilateral axial proptosis with visual loss?

Optic nerve glioma (juvenile pilocytic astrocytoma) is a slow-growing tumor of the optic nerve that causes axial proptosis. Decreased visual acuity is usually associated with a relative afferent pupillary defect. CT scan or MRI results show fusiform enlargement of the optic nerve. Many cases are associated with neurofibromatosis and may be bilateral. Systemic evaluation and genetic counseling for neurofibromatosis are essential.

14.What clinical entity is characterized by a child with rapidly progressive unilateral proptosis, displacement of the globe inferiorly, and edema of the upper eyelid?

Rhabdomyosarcoma is the most common primary orbital malignancy of childhood. This malignant growth of striated muscle tissue typically produces a rapidly progressive mass in the superior

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