Optic Neuritis

Optic neuritis is the most common acute optic neuropathy in the young. Typically the term optic neuritis denotes a demyelinating process, but can also be caused by inflammatory or infectious etiologies. The classic symptoms are subacute vision loss associated with eye pain, which is worsened with eye movements. In the Western world, multiple sclerosis (MS) is the most common cause of optic neuritis. A lot of our knowledge about optic neuritis comes from the Optic neuritis Treatment Trial (ONTT), which was a large, randomized, multicenter clinical trial evaluating treatment and prognosis of patients after acute optic neuritis. The ONTT demonstrated that intravenous corticosteroids led to a faster recovery of vision, but did not change the ultimate visual outcome. In the ONTT, 92% of patients recovered to 20/40 or better regardless of treatment. The ONTT trial also showed that 50% of patients who had optic neuritis went on to develop multiple sclerosis within 15 years, with the risk further stratified based on the presence or absence of periventricular white matter lesions on magnetic resonance imaging. Since the ONTT, two immunoglobulin G (IgG) seromarkers of atypical optic neuritis have been discovered: aquaporin-4 (AQP4)-IgG for neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein (MOG)-IgG for MOG-IgG-associated disorder. This chapter will review the epidemiology, characteristics, differential diagnosis, and treatment of optic neuritis. In addition, this chapter will compare and contrast the typical presentations of MS, AQP4-IgG positive NMOSD, and MOG-IgG-associated disorder.