Optic nerve glioma is a benign tumor that occurs in glial cells in the optic nerve. Glial cells are supporting cells of the central nervous system and ganglia. Glial cells are divided into astrocytes, oligodendrocytes and microglia. Glioma that occurs in the optic nerve is almost always an astrocytoma. Because it often occurs in fibrous astrocytes in childhood, it is also called juvenile pilocytic astrocytoma (JPA). The optic nerve is divided into 4 segments according to its location: intraocular, intraorbital, intratubular and intracranial optic nerve. Optic nerve glioma can occur in any part of the 4 segments. The intraorbital segment of the optic nerve is the longest, and gliomas originating in this segment are more common.