Optic Neuritis



  • Inflammation of the optic nerve (cranial nerve II)
  • The most common form is acute demyelinating optic neuritis (ON), but other causes include infectious disease and systemic autoimmune disorders.
  • Optic disc may be normal in appearance at onset (retrobulbar ON, 67%) or swollen (papillitis, 33%).
  • Key features:
    • Abrupt visual loss (typically monocular)
    • Periorbital pain with eye movement (90%)
    • Pain in the distribution of the first division of the trigeminal nerve
    • Dyschromatopsia: color vision deficits
    • Relative afferent pupillary defect (RAPD)
  • Usually unilateral in adults; bilateral disease more common in children
  • Associated with multiple sclerosis (MS), presenting complaint (25% MS patients)
  • In children, headaches are common.
  • System(s) affected: nervous
  • Synonym(s): papillitis, demyelinating optic neuropathy; retrobulbar ON



  • 5/100,000 cases per year
  • More common in whites than in other races
  • Predominant age: 18 to 45 years; mean age of 30 years
  • Predominant sex: female > male (3:1)

Etiology and Pathophysiology

  • In both MS-associated and isolated monosymptomatic ON, the cause is presumed to be a demyelinating autoimmune reaction.
  • Neuromyelitis optica (NMO) IgG autoantibody, which targets the water channel aquaporin-4
  • Viral infections: measles, mumps, varicella-zoster, coxsackievirus, adenovirus, hepatitis A and B, HIV, herpes simplex virus, cytomegalovirus, SARS-CoV-2 (myelin oligodendrocyte glycoprotein [MOG] antibody-associated ON and myelitis in COVID-19) (1)
  • Nonviral infections: syphilis, tuberculosis, meningococcus, cryptococcosis, cysticercosis, bacterial sinusitis, Group B Streptococcus, Bartonella, typhoid fever, Lyme disease, fungus
  • Systemic inflammatory disease: sarcoidosis, systemic lupus erythematosus, vasculitis
  • Local inflammatory disease: intraocular or contiguous with the orbit, sinus, or meninges
  • Toxic: lead, methanol, arsenic, radiation
  • Medications: ethambutol, chloroquine, isoniazid, chronic high-dose chloramphenicol, tumor necrosis factor α-antagonist, infliximab (Remicade), adalimumab (Humira), etanercept (Enbrel)

Genetics: Some people have genetic mutations that increase their chance of ON (i.e., MS) and several immune-mediated inflammatory diseases (IMIDs).

Commonly Associated Conditions

  • MS (common): ON is associated with an increased risk of MS.
  • Other demyelinating diseases: Guillain-Barré syndrome, Devic NMO, multifocal demyelinating neuropathy, acute disseminated encephalomyelitis

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