Asymmetric Outcomes in Bilateral Myelin Oligodendrocyte Glycoprotein Antibody-Associated Optic Neuritis: A Case Report

Myelin oligodendrocyte glycoprotein (MOG) antibody-associated optic neuritis (MOG-ON) usually responds well to corticosteroid treatment, even when acute visual loss is severe.We describe the case of a 60-year-old man with rapid-onset bilateral MOG-ON who was referred to our department for evaluation and treatment.At the first visit, best-corrected visual acuity (BCVA) was counting fingers in the right eye and light perception in the left eye, and a relative afferent pupillary defect was present in the left eye.Magnetic resonance imaging showed longitudinally extensive lesions of both optic nerves extending almost to the optic chiasm, with perineural enhancement of the left optic nerve.Serum anti-MOG immunoglobulin G (MOG-IgG) was positive at a titer of 1:64 on a cell-based assay.The left eye lost light perception and did not respond to intravenous methylprednisolone pulse therapy; therefore, a second course of pulse therapy and five sessions of plasma exchange were added.Although the interval from onset to treatment was shorter in the left eye, approximately five months after onset in the right eye, BCVA in logarithm of the minimum angle of resolution (logMAR) units was -0.08 in the right eye but only 0.82 in the left eye.The left eye also showed poor recovery of critical flicker fusion frequency, and a central scotoma and left-predominant macular inner retinal thinning persisted.In bilateral MOG-ON, outcomes may differ markedly between the eyes despite identical treatment.We report this case because we were able to document the longitudinal structural and functional changes in each eye.