Background: Optic nerve disease can occur from a variety of different causes, with vascular, inflammatory or toxic pathologies. In such cases, it is hardly possible to clarify the aetiology. These diseases of the optic nerve are usually accompanied by progressive loss of visual field and visual impairment. Patient: We report a case of a 74-year-old woman complaining of loss of visual acuity, visual and blurred vision in the left eye in 2010. We made the diagnosis of non-arteritic ischemic optic neuropathy (NAION). With steroid therapy, there was an improvement in both visual acuity and visual field defects. But if an attempt was made to reduce steroids, her condition progressed. Except for a very small optic disk and arterial hypotension, there were no typical risk factors for NAION. We started treatment with methotrexate (MTX), with a starting dose of 10 mg per week, and observed the patient over two years. Results: Using MTX therapy, the swelling of the optic nerve head and visual field loss were reversible, so we increased the dose of MTX up to 15 mg/week. Steroid therapy could be stopped and the patient's visual acuity and visual field have now been stable for two years. There was no visible pallor in the optic nerve head, as normally occurs after AION, so we considered different underlying pathologies, including autoimmune disease. There were no adverse events with MTX therapy. Conclusion: If the course of the disease is atypical, the pathology may include an autoimmune component. Immunosuppressive MTX therapy may be started in order to avoid long-term steroid use. It may then be possible to maintain a stable visual field and prevent remitting episodes.