Optic neuritis is a broad term expressing inflammation, degeneration, or demyelination of the optic nerve. It includes:
- papillitis or anterior optic neuritis - the intraocular portion of the nerve is affected, and the optic disc is swollen
- retrobulbar neuritis - optic neuritis in which the disc is not swollen
- neuroretinitis - optic disc and adjacent temporal retina are affected
The disc changes in papilloedema may closely resemble those of papillitis but visual acuity is reduced markedly in papillitis but not in papilloedema.
Patients usually have good outcomes with 90%+ recovering vision to 6/12 to better within 1 year which is sustained. However some abnormalities in contrast and colour sensitivity may persist
Causes/Factors
- Most commonly associated with demyelinating diseases such as Multiple Sclerosis - need to rule it out
- Metabolic - vitamin deficiencies especially of B12 severe Anaemia
- Ischaemia - Diabetes Mellitus, Giant cell arteritis, ateriosclerosis
- Familial - Leber’s disease
- Infection:
- viral - herpes zoster, Infectious mononucleosis, typhoid fever
- bacterial - neurosyphilis, Meningitis, Tuberculosis
- other - toxoplasmosis
Clinical Features
- Acute to subacute unilateral loss of vision (hours to days)
- dull aching pain in the region of the eye, aggravated by movement, especially elevation
- visual field defect - most commonly a central scotoma
- loss of colour vision - red desaturation
- relative afferent pupillary defect
- reduced visually-evoked response
- optic disc oedema
Investigations
- Visual field testing
- Colour vision assessment
- Fundoscopy
- Test eye movements
- Blood tests - autoimmune markers, ESR, infection & inflammatory markers
- MRI of brai and orbits with gadolinium contrast - shows lesions of optic nerve. May also show white matter lesions suggestive of MS. LP may support that
Management
Oral Prednisolone was found to be ineffective and increased the risk of recurrence
The typical regimen is intravenous methylprednisolone 1g daily for three days followed by an oral Prednisolone taper (1mg/kg for 11 days).
Oral methylprednisolone 500mg once a day for five days has been suggested as an alternative to intravenous steroids, but its use remains controversial.
Info
Treatment is more likely to be offered to those with a diagnosis of MS, profound visual loss in a solitary eye, or in cases of severe pain.3 It is important to consider the significant side effects which can be associated with high-dose steroids, and counsel the patient appropriately.
Complications/red Flags
- Risk of recurrence in the affected or other eye is about 30% at 5 years
- An episode of ON does not imply a definite conversion to MS. Data from the ONTT shows that the overall 15-year risk of developing MS is 50%