Idiopathic orbital inflamatory syndrome (IOIS)

Alternative names
Orbital pseudotumor

The orbit is the bony pyramid-shaped cavity of the skull that contains and protects the eyeball and associated structures. Orbital pseudotumor is a swelling of the orbital tissues behind the eye, but unlike cancerous tumors, it cannot invade tissues or spread elsewhere.

Causes, incidence, and risk factors

The cause is unknown. No risk factors are known.


Swelling of the tissue around the eye with bulging of the eye, often painful.

Signs and tests

The changes of pseudotumor can be seen when the eye is examined. Tests to differentiate a pseudotumor from a tumor include the following:

  • Ultrasound  
  • X-ray  
  • Biopsy


Mild cases may regress without treatment. More severe cases will usually respond to treatment with corticosteroids. Very severe cases may develop damaging pressure on the eye and require surgical movement of the bones of the orbit to decompress the eyeball.

Expectations (prognosis)

Most cases are mild and do well. Severe cases may be resistant to treatment and visual loss may occur. Orbital pseudotumor usually involves only one eye.


Severe cases of orbital pseudotumor may push the eye forward to the extent that the lids can no longer protect the cornea, and damage to cornea clarity or corneal ulcer may occur. The eye muscles may not be able to properly aim the eye, and double vision may result.

Calling your health care provider

Patients with pseudotumor will be closely followed by an ophthalmologist with experience in treatment of orbital disease.

If you experience irritation of the cornea, redness, pain, or decreased vision, call your ophthalmologist or general health care provider right away.

Johns Hopkins patient information

Last revised: December 5, 2012
by Potos A. Aagen, M.D.

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