Higher magnification showing long, delicate hair-like processes and bland nuclei. Optic nerve gliomas are grade I astrocytomas that can cause significant morbidity given their location. They rarely extend into the orbit or undergo malignant transformation. In the setting of NF1, however, they sometimes break through the pia and proliferate within the subarachnoid space (arachnoidal gliomatosis). Many optic nerve gliomas are followed conservatively. In cases with high degree of proptosis, surgical resection of the optic nerve or enucleation may be done. Association with NF1 or involvement of optic chiasm are adverse prognostic factors.