A 36-year-old man presented with an acute onset of a right eye monocular altitudinal defect associated with pain on eye movement upon waking up from sleep. His right eye subsequently developed outward deviation and a total loss of vision. Clinical examination of the right eye revealed a visual acuity of no light perception (NLP) with the presence of relative afferent pupillary defect (RAPD) and involvement of cranial nerves II, III, IV, and VI. A marked optic disc swelling and peripapillary hemorrhages were seen in the right fundus. Contrast-enhanced computed tomography of the brain and orbit showed a unilateral enlargement and enhancement of the right intraorbital and intracanalicular segments of the optic nerve with surrounding fat stranding and orbital apex crowding. Magnetic resonance imaging showed T2/fluid-attenuated inversion recovery hyperintensity and enhancement of the optic nerve and the myelin sheath. Serum anti-myelin oligodendrocyte glycoprotein antibodies were detected. He was treated with corticosteroids, plasma exchange, and intravenous immunoglobulin. His vision improved slowly after treatment. This case report shows the diverse manifestations of myelin oligodendrocyte glycoprotein antibody disease, which includes the orbital apex syndrome.