A 36-year-old woman with bilateral optic neuropathy and orbital and central nervous system metastasis from breast carcinoma developed progressive bilateral vision loss with severe optic disc swelling. She underwent optic nerve sheath fenestration of the left eye resulting in modest improvement in vision and resolution of disc edema. Optic nerve sheath fenestration is a known treatment for papilledema, but its effectiveness as a treatment for an optic neuropathy caused by perineural or intrasheath metastasis is less clear. Optic nerve sheath fenestration should be considered as a treatment option for an optic neuropathy caused by perineural or intrasheath metastasis, especially in cases where alternative treatments are not tolerated and visual loss is severe at presentation.