Computed tomography (CT) scan of orbits showing bilateral optic nerve gliomas. These are glial cell derived tumours arising from the optic nerve, usually presenting in childhood. Roughly 50% are associated with neurofibromatosis 1. Clinical manifestations include decreased visual acuity, exophthalmos, nystagus, strabismus, pallor or swelling of the optic disc; and intracranial hypertension. The tumour may extend into the optic chiasm and hypothalamus.