A 69-year old man presented to us with decreased vision in his right eye and a relative afferent pupillary defect. Under the presumption that he was suffering from retrobulbar optic neuritis or ischemic optic neuropathy, visual field tests were performed, revealing the presence of a junctional scotoma. Imaging studies revealed tumorous lesions extending from the sphenoid sinus at the right superior orbital fissure, with erosion of the right medial orbital wall and optic canal. Right optic nerve decompression was performed via an endoscopic sphenoidectomy, and histopathologic examination confirmed the presence of aspergillosis. The patient did not receive any postoperative antifungal treatment; however, his vision improved to 20 / 40, and his visual field developed a left congruous superior quadrantanopsia 18 months postoperatively. A junctional scotoma can be caused by aspergillosis, demonstrating the importance of examining the asymptomatic eye when a patient is experiencing a loss of vision in one eye. Furthermore, damage to the distal optic nerve adjacent to the proximal optic chiasm can induce unusual congruous superior quadrantanopsia.