Orbital Inflammatory Pseudotumor

During a routine eye examination for contact lenses, a visual field defect was found in the left eye of a 27-year-old man. The patient had not noticed any vision changes. His history was unremarkable, and he considered himself healthy. He occasionally used an over-the-counter acne cream. He drank alcohol socially and did not smoke. His father had cataracts.

The patient's best corrected visual acuity with his contact lenses was 20/20 in each eye. He had no afferent pupillary defect, and color vision testing results were normal. A slit-lamp evaluation was unremarkable. A dilated fundus examination showed a normal optic nerve with a cup-to-disc ratio of 0.1 in the right eye (A). The left optic nerve showed temporal pallor and a cup-to-disc ratio of 0.4 (B). The results of a computerized visual field test were normal in the right eye, but the left eye showed a depressed visual field in the infratemporal quadrant (C and D).

Because of the optic atrophy and visual field defect, MRI evaluation was ordered. Findings on an MRI scan of the brain were normal. An MRI scan of the orbits revealed mild enhancement of the left inferior medial optic nerve sheath and the adjacent medial intraconal fat (E). These findings ruled out optic neuritis.

Orbital inflammatory pseudotumor was suspected, and the patient began a course of IV methylprednisolone, 1 g/d, on an outpatient basis, followed by a tapering course of oral prednisone for 7 days. An orbital MRI scan 6 weeks later showed overall improvement in the gadolinium enhancement pattern of the optic nerve sheath and intraconal fat. Minimal residual inflammation was still present. A second visual field test revealed that the defect had not worsened. The patient is being monitored every 6 months.

Orbital inflammatory pseudotumor is a nongranulomatous inflammatory disorder that has no known cause or systemic associations. This unilateral orbital lesion may compress orbital structures, with resulting optic neuropathy or cranial nerve palsies. Orbital pain, conjunctival chemosis, eyelid swelling, and proptosis often result.

Orbital imaging, especially contrast-enhanced MRI, is the test of choice. Because orbital inflammatory pseudotumor is a diagnosis of exclusion, other conditions, such as diabetes, sinusitis, connective tissue diseases, and sarcoidosis, must be ruled out.

Orbital inflammatory pseudotumor responds dramatically to corticosteroids; signs and symptoms remit within days. Corticosteroid responsiveness is considered a diagnostic feature of this disease. Radiation therapy may be effective for those patients who do not respond to corticosteroids.