Optic Neuritis
The concept of optic neuritis (ON) refers to inflammatory processes affecting the optic nerve and is a clinical term.
Classically, the term optic neuritis is reserved for demyelination of the optic nerve. It is a condition that more frequently affects young women and has an incidence of approximately 5 per 100,000 inhabitants. Typically, the patient presents with acute unilateral vision loss and pain with eye movements. The degree of visual loss can range from very mild to severe. Ocular pain occurs in approximately 90% of patients. In unilateral neuritis, there will be a relative afferent pupillary defect. Symptoms usually begin to improve after two weeks.
Most cases of optic neuritis are retrobulbar, meaning that the optic nerve appears normal on funduscopic examination during the acute stage. The most commonly found visual field defect is a reduction in overall sensitivity, and color vision is typically impaired. Visual evoked potentials show delayed latency.
Causes
Idiopathic, post-infectious, demyelinating, among others.
Symptoms
- Decreased vision
- Dyschromatopsia (color vision disturbance)
- Visual field defects
Diagnosis
All patients with optic neuritis should undergo magnetic resonance imaging (MRI) to rule out associated systemic demyelinating disease and to assess the risk of developing multiple sclerosis. A lumbar puncture should also be performed to detect the presence of oligoclonal bands.
Other conditions must be ruled out in atypical cases, such as when the patient falls outside the usual age range, when the clinical course does not follow a typical pattern, when neuritis is bilateral and simultaneous, or when atypical symptoms are present.
Visual prognosis is generally good. Patients typically begin to recover visual acuity about two weeks after symptom onset. Persistence of symptoms over time should alert the physician to the possibility of an alternative diagnosis.
Treatment
Treatment consists of high-dose intravenous corticosteroids. In cases associated with multiple sclerosis, immunomodulatory therapy is indicated.
Other Forms of Neuritis
Neuromyelitis Optica (Devic’s Disease):
Optic neuropathy associated with transverse myelitis presents as severe bilateral optic neuropathy in young adults, with a less predictable prognosis compared to typical optic neuritis.
Diagnosis is based on the following criteria:
- Contiguous spinal cord lesions extending over at least three vertebral segments
- MRI findings not compatible with multiple sclerosis
- Seropositivity for NMO-IgG (aquaporin-4 antibodies)
Initial treatment includes corticosteroids. Plasmapheresis and immunomodulatory therapies are also used.
Anti-MOG Antibody-Associated Optic Neuritis:
This is another type of optic neuritis associated with the presence of anti-MOG antibodies. It may present bilaterally. Treatment consists of high-dose corticosteroids and plasmapheresis during the acute phase.