What is optic neuritis?

Optic neuritis is a medical term to describe inflammation of the optic nerve. The optic nerve is the nerve of vision – the pathway that carries messages from the eye to the brain. There is an association between optic neuritis and MS but not all people who have optic neuritis go on to develop MS.  

What are the symptoms of optic neuritis?

Optic neuritis tends to come on over a few days. Sometimes, though, symptoms occur quickly, either over a few hours or people wake up with their vision affected. For people with MS, optic neuritis tends to affect one eye but it can affect both eyes, too, either at the same time or one after another.

Most people with optic neuritis say it is painful when they move their eyes but the pain should not affect sleep. (If the pain is more severe than this, then it might be something else and need further investigation.) Pain rarely lasts more than a few days. The severity of pain can be different for different people and about 10 per cent of people say they do not experience any pain.

The effect on vision can also vary in optic neuritis. It can range from blurring of vision to someone having ‘no perception of light’ (sight loss) in the affected eye or eyes. There might be a blurring or blankness in the centre of sight. Colour vision is also usually affected; colours are described as being darker or washed out. Some people have light flashes (called ‘phosphenes’) when they move their eyes.
 

How is optic neuritis diagnosed?

Doctors will usually diagnose optic neuritis by asking about a person’s history and observing typical signs. Electrical testing of how the optic nerves are working (‘visual evoked potentials’) or scans of the optic nerves can sometimes help as well. Some other eye conditions can mimic optic neuritis, though, so if symptoms are not typical, other investigations should be done. Signs that might indicate some other cause for the loss of vision include severe pain that restricts eye movement or wakes a person from sleep, having no pain at all, severe vision loss in both eyes, or when vision might not start to improve by itself after three to four weeks. This is not a full list – do ask your doctor if you are worried.  

Recovery from optic neuritis

Most people recover well from optic neuritis. In one of the key clinical trials for optic neuritis, 79 per cent of people showed signs of improvement within three weeks, and 93 per cent began to recover within five weeks. Further improvement in vision can happen up to a year after symptoms begin.

Following optic neuritis, vision tends to recover by itself. The early stages of recovery can be rapid, probably because it relates to inflammation of the optic nerve going down. Remyelination of the optic nerve, where the body repairs damaged myelin around the nerve, can also be responsible for later recovery of vision after optic neuritis.

Frequently, people remark that their vision in the affected eye or eyes is not quite as it was. There might be subtle things to do with picking up colour or colour contrasts, depth perception or some loss of visual sharpness, even though a test might say that their vision is still within normal limits.

After optic neuritis, vision can also vary during the day (say, different in the mornings to evenings) and from one day to the next. People might experience eye strain or a ‘fading of vision’. Heat or exercise might make vision temporarily worse – this is very common generally amongst people with MS and is called ‘Uhthoff’s phenomenon’.  

Treatment for optic neuritis

Occasionally, steroids are used for the treatment of optic neuritis. Steroids may be given either as tablets or as a drip. Clinical trials have shown that steroids can speed up the recovery of vision but they do not seem to affect how well a person recovers their sight in the long-term.

The decision about whether or not to use steroids should be made between the doctor and the person with optic neuritis. In a typical case of optic neuritis, a ‘wait-and-see’ approach is reasonable. However, some people want a more rapid recovery of vision, especially if both eyes are affected.

If recovery from optic neuritis is not good, at present there is no treatment that can reverse this. Poor vision caused by optic neuritis cannot be helped with glasses or eye exercises. Future therapies to improve vision might include treatments to protect the optic nerve (‘neuroprotection’), treatments to promote remyelination, or possibly optic nerve transplantation. All of these are experimental at present.  

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