Optic neuritis is an inflammation of the nerve at the back of the eye. There are many potential causes as well as cases where there is no explanation. In some this may occur in association with multiple sclerosis, or may be indicative of previously undiagnosed multiple sclerosis.
Other potential causes are:
- Diabetes in younger patients
- Viral infection e.g. glandular fever, Herpes Zoster or immunization
- Associated bacterial infections: Cat scratch disease, Lyme disease, Syphilis
- Sinus infection
- Vasculitis – Inflammation of blood vessels
- Demyelination – Multiple Sclerosis
(In many of the cases above the symptoms will not fit this pattern and may be quite variable)
- Typically the vision deteriorates (often profoundly) over a period of days, usually in one eye and being worst after ten days, after which there is a gradual recovery over six weeks.
- Colour vision appears washed out.
- Light intensity is reduced in the affected eye.
- There may be changes to binocular vision and the vision may get worse when warm, for example in a bath or when exercising.
- There is often pain behind the eye or associated with eye movement.
It is important to exclude a mass pressing on the nerve, or further back in the brain. Additionally causes such as the above will need to be excluded.
Accordingly, a range of tests including:
- CT scan, MRI and X rays may be required.
- Blood tests.
- Lumbar puncture.
If the vision loss is mild and not progressing, observation alone may suffice.
When there is profound loss of vision, and this is caught early, intravenous steroids may be offered. These have been shown to hasten resolution.
In around half of cases, an underlying cause is excluded and there are no further occurrences. In some cases there is underlying demyelination as in MS, which will be discussed with a view to future management.