Optic nerve gliomas and meningiomas. Optic nerve gliomas are benign astrocytic neoplasms that primarily affect children. The ultimate prognosis for vision is poor. For lesions confined to the optic nerves, long-term survival is excellent, but with involvement of the chiasm and especially of the hypothalamus or third ventricle, prognosis falls significantly. For this group, no form of therapy has proven to be of any benefit. Optic sheath meningiomas are neoplasms arising from arachnoid cap cells. They primarily affect middle-aged adults. Like gliomas, the prognosis for vision is poor, but unlike gliomas, prognosis for life is excellent. 