An optic nerve glioma is a type of brain tumor. There are multiple kinds of brain tumors. Typically, each type of tumor is named after the kinds of cells it affects. Most optic nerve gliomas are considered low-grade and don’t grow as quickly as other types of brain tumors. They are found in the optic chiasm, where the left and right optic nerves cross. They are also referred to as optic glioma or juvenile pilocytic astrocytoma.