Optic Neuritis in a Patient with Morning Glory Syndrome: A Case Report

Purpose: To describe a rare case of optic neuritis in a Morning glory syndrome (MGS) patient and to highlight the diagnostic challenges posed by congenital optic disc anomalies.Case summary: A 45-year-old woman presented with a 5-day history of an inferonasal visual field defect, blurred vision, and ocular pain in the right eye. Best-corrected visual acuity was 20/20 in both eyes; however, a relative afferent pupillary defect (RAPD) was detected in the right eye. Fundus examination revealed a morning glory disc anomaly, and visual field testing demonstrated blind spot enlargement with an inferonasal defect. Magnetic resonance imaging showed focal T2-weighted high signal intensity with mild gadolinium enhancement in the retrobulbar optic nerve, without lesions, suggestive of multiple sclerosis or neuromyelitis optica. The patient was diagnosed with retrobulbar optic neuritis and treated with high-dose intravenous methylprednisolone. Following treatment, both the visual field defect and RAPD showed improvement.Conclusions: MGS is a rare congenital anomaly characterized by a funnel-shaped excavation of the optic disc and anomalous peripapillary vasculature. These structural abnormalities may obscure typical clinical signs of optic neuritis, such as optic disc swelling, thereby complicating early diagnosis. In this case, the diagnosis was supported primarily by the presence of RAPD, visual field abnormalities, and magnetic resonance imaging. This report demonstrates the importance of multimodal evaluation, particularly magnetic resonance imaging, in assessing acute vision loss in eyes with congenital optic disc anomalies. To our knowledge, this is the first reported case of optic neuritis associated with MGS in South Korea.