A differential diagnosis includes lymphoproliferative lesions, thyroid ophthalmopathy, IgG4-related ophthalmic<unk> , sarcoidosis, granulomatosis with polyangiitis, orbital cellulitis and carotid-cavernous fistula. Imaging The best imaging modality for<unk>  is contrast-enhanced thin section magnetic resonance with fat suppression. The best diagnostic clue is a poorly marginated, mass-like enhancing soft tissue involving any area of the orbit. Overall, radiographic features for<unk>  orbital<unk>  syndrome vary widely. They include inflammation of the extraocular muscles (myositis) with tendinous involvement, orbital fat stranding, lacrimal gland inflammation and enlargement (dacryoadenitis), involvement of the optic sheath complex, uvea, and sclera, a focal intraorbital mass or even diffuse orbital involvement. Bone destruction and intracranial extension is rare, but has been reported. Depending on the area of involvement, IOI may be categorized as: * Myositic * Lacrimal * Anterior – Involvement of the globe, retrobulbar orbit * Diffuse – Multifocal intraconal involvement with or without an extraconal component * Apical – Involving the orbital apex and with intracranial involvement Tolosa–Hunt syndrome is a variant of orbital pseudotumor in which there is extension into the cavernous sinus through the superior orbital fissure. Another<unk>  variant is Sclerosing pseudotumor, which more often presents bilaterally and may extend into the sinuses. CT findings In non-enhanced CT one may observe a lacrimal, extra-ocular muscle, or other orbital mass. It may be focal or infiltrative and will have poorly circumscribed soft tissue. In contrast-enhanced CT there is moderate diffuse irregularity and enhancement of the involved structures. A dynamic CT will show an attenuation increase in the late phase, contrary to lymphoma where there is an attenuation decrease. Bone CT will rarely show bone remodeling or erosion, as mentioned above. MR findings On MR examination there is hypointensity in T1 weighted imaging (WI), particularly in sclerosing<unk> . T1WI with contrast will show moderate to marked diffuse irregularity and enhancement of involved structures. T2 weighted imaging with fat suppression will show iso- or slight hyperintensity compared to muscle. There is also decreased signal intensity compared to most orbital lesions due to cellular infiltrate and fibrosis. In chronic<unk>  or sclerosing variant, T2WI with FS will show hypointensity (due to fibrosis). Findings on STIR (Short T1 Inversion Recovery) are similar to those on T2WI FS. In Tolosa–Hunt syndrome, findings include enhancement and fullness of the anterior cavernous sinus and superior orbital fissure in T1WI with contrast, while MRA may show narrowing of cavernous sinus internal carotid artery (ICA). Ultrasonographic findings On grayscale ultrasound there is reduced reflectivity, regular internal echoes, and weak attenuation, in a way, similar to lymphoproliferative lesions.
Idiopathic orbital inflammatory disease
Orbital lymphoma
Orbital cellulitis
Neurotrophic keratitis
Ocular ischemic syndrome
Phacolytic glaucoma
Acute hemorrhagic conjunctivitis
Intraocular lymphoma