Snapshot A 33-year-old woman presents to the emergency department for severe eye pain with movement and vision loss in the left eye. Her symptoms began earlier in the morning and she cannot identify a cause. Physical examination is notable for a relative afferent pupillary defect noted on the swinging light test. She is scheduled for a gadolinium-enhanced MRI of the orbit and the globe; she is started on intravenous methylprednisolone. Introduction Definition an inflammatory demyelinating process affecting the optic nerve Pathogenesis inflammatory demyelination of the optic nerve there is perivascular cuffing, myelinating nerve sheath swelling, and myelin breakdown believed to be immune mediated Epidemiology Incidence most commonly affects women between the ages of 20-40 Etiology multiple sclerosis ethambutol discontinue if findings ischemic optic neuropathy (e.g., diabetes mellitus or giant cell arteritis) considered in the elerly infectious and postinfectious causes considered in young children sarcoid-associated optic neuropathy lupus-associated optic neuropathy Lyme disease syphilis varicella Presentation Symptoms typically monocular but can occur in both eyes vision loss typically occurs over the course of hours to days most patients have a decrease in central visual acuity visual acuity decreases have different ranges periocular pain often worsens with movement Physical exam decreased visual acuity, color sensitivity, and contrast sensitivity fundoscopy optic disc pallor and/or optic disc swelling relative afferent pupillary defect detected by the swinging light test in the affected eye, the pupil will dilate with direct illumination after illuminating the normal eye Imaging Gadolinium-enhanced MRI of the orbit and brain indication when there is clinical suspicion for multiple sclerosis Studies Dependent on clinical suspicion e.g., antinuclear antibody (ANA) if an autoimmune process is suspected Treatment Medical high-dose IV corticosteroids indication can hasten visual recovery Complications Optic nerve atrophy Poor visual recovery Prognosis Many patients may have residual visual deficits