This is a common, non-neoplastic, acute or chronic inflammatory condition. It may be diffuse, involving widespread areas of orbital fat, or localized to specific structures such as the sclera, one or more extraocualr muscles, or the lacrimal gland. Patients present with inflammatory symptoms including pain, conjunctival injection, eyelid edema, proptosis, and decreased ocular motility. Visual disturbance can be seen when the optic nerve sheath is involved. Systemic steroids produce resolution in more than half of cases as does low dose radiotherapy.