Optic nerve sheath meningiomas (ONSM) are rare, slow-growing, benign tumors of the meninges surrounding the optic nerve. These tumors are classically found in adults after the third decade of life, are rare in children, and occur more commonly in women than in men (3:2 ratio). Most patients will present with progressive monocular vision loss. Patients may also experience loss of color vision (dyschromatopsia), headache, and soreness in the eye. Optic atrophy and relative afferent pupillary defect may be seen on examination. ONSM is frequently mistaken for optic neuritis. Risk factors include prior radiation therapy exposure for central nervous system malignancies, incidental radiation exposure, and genetic conditions such as neurofibromatosis type 2 and schwannomatosis.

Treatment is often complicated and limited by the location of the tumor and can result in significant complications such as visual impairment and blindness. Morbidity from ONSM is low but the prognosis for visual recovery is variable, with many patients losing vision in the affected eye.