CSF = cerebrospinal fluid, EDSS = Expanded disability status scale, HC = healthy controls, GC-ON = glucocorticoid responsive optic neuritis, MIF = Macrophage migration inhibitory factor, MS w/o = Clinically isolated syndrome or multiple sclerosis without an acute relapse, ON = acute optic neuritis group, rGC-ON = non-glucocorticoid-responsive optic neuritis.