The exact cause of IOI is unknown, but infectious and immune-mediated mechanisms have been proposed. Several studies have described cases where onset of orbital pseudotumor was seen simultaneously or several weeks after upper respiratory infections. Another study by Wirostko et al. proposes that organisms resembling Mollicutes cause orbital inflammation by destroying the cytoplasmic organelles of parasitized cells. Orbital pseudotumor has also been observed in association with Crohn’s<unk> , systemic lupus erythematosus, rheumatoid arthritis, diabetes mellitus, myasthenia gravis, and ankylosing spondylitis all of which strengthen the basis of IOI being an immune-mediated<unk> . Response to corticosteroid treatment and immunosuppressive agents also support this idea. Trauma has also been seen to precede some cases of orbital pseudotumor. However, one study by Mottow-Lippe, Jakobiec, and Smith suggests that the release of circulating antigens caused by local vascular permeability triggers an<unk>  cascade in the affected tissues. Although these mechanisms have been postulated as possible causes of IOI, their exact nature and relationships to the condition still remain unclear. Histopathology The histopathology of<unk>  orbital inflammation is described as nondiagnostic and diverse. It includes diverse polymorphous infiltrate, atypical granulomatous inflammation, tissue eosinophilia, and infiltrative sclerosis Although several classification schemes have been postulated, none have been definitively accepted due to the absence of distinct differences among the histopathological types as to the signs, symptoms, clinical course, and outcome.
Idiopathic orbital inflammatory disease
Orbital lymphoma
Orbital cellulitis
Neurotrophic keratitis
Ocular ischemic syndrome
Phacolytic glaucoma
Acute hemorrhagic conjunctivitis
Intraocular lymphoma