Definition: Glial cell derived tumors arising from the optic nerve, usually presenting in childhood. Roughly 50% are associated with NEUROFIBROMATOSIS 1. Clinical manifestations include decreased visual acuity; EXOPHTHALMOS; NYSTAGMUS; STRABISMUS; pallor or swelling of the optic disc; and INTRACRANIAL HYPERTENSION. The tumor may extend into the optic chiasm and hypothalamus. (Adams et al., Principles of Neurology, 6th ed, p681)