Optic neuritis (ON) is a debilitating condition that is defined as inflammation of cranial nerve II which results in disruption of the neurologic pathways that allow visual sensory information received by the retina to be able to be transmitted to the visual cortex of the brain. This disorder of the optic nerve may arise through various pathophysiologic mechanisms, such as through demyelination or inflammation, leading to partial or total loss of vision. Although pain is typically considered a hallmark feature of optic neuritis, the absence of pain does not preclude a diagnosis or consideration of ON as some patients may report painlessness. Other etiologies include idiopathic ON, infections (e.g., syphilis, Lyme disease, and viral infections such as herpes simplex and varicella-zoster), and systemic autoimmune diseases (e.g., systemic lupus erythematosus and sarcoidosis). Atypical ON essentially refers to optic neuritis from any other cause.

Idiopathic Disease

Idiopathic optic neuritis (ION) generally refers to optic neuritis that does not present with serologic markers attributable to a known underlying cause (e.g., NMOSD, MOGAD, etc.). Opinions among specialists seem to differ as to whether idiopathic optic neuritis should be classified as MS-associated ON or if it should not be exclusively associated with MS. A group of reviewers from China propose that ION should not be associated with MS and hence defined with the literal meaning of "idiopathic" as ON with an unknown cause. Other causes of atypical ON include myelin oligodendrocyte glycoprotein-antibody-associated disease (MOGAD), other autoimmune disorders (e.g., Sarcoidosis, Sjogren syndrome, rheumatoid arthritis, systemic lupus erythematosus), and infections (Bacterial [<nowiki/>Tuberculosis, syphilis, meningitis, Lyme's disease, Bartonella] or Viral [<nowiki/>measles, mumps, rubella, chicken pox, herpes]). The hallmark diagnostic criteria of NMOSD is the presence of the aquaporin-4 immunoglobulin G antibodies (AQP4-IgG) found on serology, which is the underlying aberrancy of this autoimmune condition that engenders its distinction from multiple sclerosis. Cell-mediated and complement-mediated inflammation results hallmark findings of perivenous and confluent white matter demyelination. The pathogenesis of ON secondary to HIV has been proposed to arise from autoimmune, vascular, and degenerative ischemic pathways.

When an inflammatory recurrent optic neuritis is not demyelinating, it is called chronic relapsing inflammatory optic neuropathy (CRION).

Signs and symptoms

Major symptoms are:

  • sudden loss of vision (partial or complete),
  • sudden blurred or "foggy" vision, and
  • pain on movement of the affected eye.

Patients with optic neuritis may experience dyschromatopsia which describes a range of color vision in the affected eye (especially red), with colors appearing subtly washed out compared to the other eye. Patients may also experience difficulties judging movement in depth, which can be particular troublesome during driving or sport (Pulfrich effect). Likewise, transient worsening of vision with increase of body temperature (Uhthoff's phenomenon) and glare disability are a frequent complaint.

Involvement of the optic nerve may be unilateral or bilateral, depending on the underlying etiology.

Early Symptoms

Early symptoms that require investigation include symptoms from multiple sclerosis (twitching, lack of coordination, slurred speech, frequent episodes of partial vision loss or blurred vision), episodes of "disturbed/blackened" rather than blurry indicate moderate stage and require immediate medical attention to prevent further loss of vision. Other early symptoms are reduced night vision, photophobia and red eyes.

Variation in symptoms with age

Several case studies in children have demonstrated the absence of pain in more than half of cases (approximately 60%) in their pediatric study population, with the most common symptom reported simply as "blurriness". Other remarkable differences between the presentation of adult optic neuritis as compared to pediatric cases include more often unilateral optic neuritis in adults, while children much predominantly present with bilateral involvement.

Diagnosis

The World Health Organization's ICD-11 classification includes optic neuritis. In practice, optic neuritis is diagnosed by a combination of features pertaining to symptom manifestation, clinical evaluation, and imaging findings.

Clinical Evaluation

A trained healthcare provider may evaluate a patient for optic neuritis by identifying the presence and degree of visual acuity loss, visual field loss, color vision deficits, and an afferent pupillary defect in the affected eye.

Fundoscopy is another modality of clinical evaluation that is performed with an ophthalmoscope. Findings that support a diagnosis of optic neuritis include optic disc edema, disc inflammation, disc hemorrhages, or ocular inflammation. Another study found that T2-weighted images with fat suppression and short tau inversion recovery (STIR) detected lesions in up to 89% of acute optic neuritis cases with abnormalities persisting for as long as 6 weeks in 92% of cases.

thumb|Magnetic Resonnance Imaging (MRI) during an episode of optic neuritis.

Identification of optic nerve, orbital, brain, and meningeal involvement with MRI can also help to better characterize the underlying cause of optic neuritis upon initial evaluation. Unilateral optic nerve involvement is more common MS while bilateral optic nerve involvement is more common in NMOSD and MOGAD. A good diagnosis depends on timing. For OCT, the mGCIPL is most sensitive in the chronic phase. This matters when testing is needed to confirm optic nerve involvement for dissemination in space (DIS) in MS.

New advancements in OCT technology have allowed for the development of OCT angiography which can provide information on the thickness of retinal blood vessels. Whereas OCT has yet to demonstrate identifiable correlations between acute RNFL changes and visual outcomes or treatment responses, OCT angiography may offer novel diagnostic and prognostic insight.

VEP

Visual evoked potential (VEP) is a sensitive test that measures the P100 latency of axonal transmission along the optic nerve. The P100 latency typically peaks at 100 milliseconds after visual stimulus presentation, and a prolonged P100 latency suggests abnormal conduction along this pathway which confirms the presence of optic neuropathy.

Steroids

High dose steroids may be given intravenously (IV) or orally, though IV steroids such as methylprednisolone are typically recommended.

Paradoxically, oral administration of corticosteroids in this situation may lead to more recurrent attacks than in non-treated patients (though oral steroids are generally prescribed after the intravenous course, to wean the patient off the medication). This effect of corticosteroids seems to be limited to optic neuritis and has not been observed in other diseases treated with corticosteroids.

A Cochrane systematic review studied the effect of corticosteroids for treating people with acute optic neuritis. Specific corticosteroids studied included intravenous and oral methylprednisone, and oral prednisone. The authors conclude that current evidence does not show a benefit of either intravenous or oral corticosteroids for rate of recovery of vision (in terms of visual acuity, contrast sensitivity, or visual fields).

Immunosuppressants

Immunosuppressants may also be used in treatment.

Society and culture

In Charles Dickens' Bleak House, the main character, Esther Summerville, has a transient episode of visual loss, the symptoms of which are also seen in people who have optic neuritis. Legal historian William Searle Holdsworth suggested that the events in Bleak House took place in 1827.

In an episode of Dr. Quinn, Medicine Woman ("Season of Miracles", season five), Reverend Timothy Johnson is struck blind by optic neuritis on Christmas Day 1872. He remains blind for the duration of the series.

See also

  • Optic neuropathy
  • Visual snow

References

  • Diagnosis and classification of optic neuritis, translated into 116 languages and free for download