More Common

Thyroid orbitopathy (often spares tendon), idiopathic orbital inflammatory syndrome (involves tendon).

Less Common

Tumor (e.g., lymphoma, metastasis, or spread of lacrimal gland tumor to muscle), c-c fistula, superior ophthalmic vein thrombosis, cavernous hemangioma (usually appears in the muscle cone without muscle thickening), rhabdomyosarcoma (children).

More Common

Optic nerve glioma (especially children), optic nerve meningioma (especially adults).

Less Common

Metastasis, leukemia, idiopathic orbital inflammatory syndrome, sarcoidosis, increased intracranial pressure with secondary optic nerve swelling.