This national investigation will be conducted to describe the epidemiology and clinical characteristics of optic neuritis in China. All the patients will be divided into 3 groups according to the serum demyelinating antibodies (Aquaporin-4 antibody seropositive group, Myelin oligodendrocyte glycoprotein antibody seropositive group and double seronegative group). The investigator will analyze the differences among the three groups.

Primary outcomes:

• To dig out the different visual acuity (VA, LogMAR) prognosis among the three groups;
• To calculate the annual relapse rate (ARR) differences among the three groups (relapse times in all the follow-up time in each group/ follow-up time (years) in all in each group).

Secondary outcomes:

• Other epidemiological and clinical characteristics of optic neuritis patients will be analyzed among the three groups;
• Orbital or Brain MRI is required in this study, which could avoid the misdiagnosis. We will collect and analyze these MRI data too (including the optic nerve lesions in T2 weight images and T1 enhanced MRI);
• Results of optical coherence tomography (OCT) (including peripapillary retinal nerve fiber layer, macular thickness ,and ganglion cell and inner plexiform layer complex) at different time point are also needed in this study. However, OCT is not necessarily required;
• Visual fields at different time points are also encouraged to provide if they are available.