Optic neuritis

What is called optic neuritis is probably the most common visual symptom of MS, perhaps appears in 50% of people with MS, and indeed may well appear before any other symptoms of the disease are obvious. Optic neuritis (inflammation of the optic nerve, which is at the back of the eye) may result in various kinds of vision loss or difficulty. The acute form may result in temporary loss or disturbance of vision in one eye, and very occasionally vision loss at the same time in both eyes – although one eye may follow the other in being affected. Vision loss or disturbance may most often be in the centre of the eye, but it may also be in peripheral vision. Chronic optic neuritis can result in a range of continuing visual symptoms. Even those people with normal sharpness of vision (visual acuity) may have a reduced capacity to deal with contrasts in their visual field, or have reduced colour vision.
When such a symptom appears, it can be a very worrying development for people with MS – as can be expected in anyone if a sudden loss of vision occurs. In almost all cases vision reappears and is often almost back to normal after a period of time. However, this process may take several weeks. Symptoms of optic neuritis can worsen for up to 2 weeks after its initial onset, then most people recover rapidly and have improved back to their pre-attack state after 5 weeks. Recovery in a very few cases may take up to a year. Some people who have had an attack may feel that the quality of their vision is not quite as it was, and they can be left with some problems in relation to colour vision, depth perception and contrast sensitivity. Optic neuritis can also be present without any obvious major symptoms, although on careful checking minor abnormalities can often be detected in such cases.
It is important to say that there are a range of other conditions that may result in condiditons similar to optic neuritis. In relation to MS itself there is strong link between the presence of optic neuritis and the disease in the form of CNS lesions – mostly the larger the number of lesions detected by MRI the more likely MS is the cause.

Treating optic neuritis
Corticosteroids have been the main basis of medical treatment for optic neuritis for some time, even though there is conflicting research about the effectiveness of their use. The basis of the use of these drugs is that they have some effect on the immune system. In relation to what can be described as inflammatory eye disease, it is thought they could help in reducing the inflammation. A combination of methylprednisolone and prednisone may be given, although this may vary. Because in most cases (even the most severe), vision returns to something like its previous state in a reasonable period of time, some neurologists are reluctant to give powerful steroid drugs, which can have significant side effects. So, although it is worrying for people with a sudden onset of these symptoms, waiting for the return of vision or the lessening of visual disturbances is often the strategy that is followed.
With the advent of beta-interferon type drugs in MS (where optic neuritis can be one symptom), there has been increasing pressure to give such drugs at an earlier stage in the condition. In principle, if the MS could be detected earlier – and optic neuritis is a frequent symptom occurring before MS has been diagnosed – then optic neuritis would probably be a symptom that responded to such a treatment. However, definitively diagnosing MS at such an early stage may not be easy, and there is still much debate about how appropriate the beta-interferons are to give to all people at that stage of MS.

Eye movement abnormalities

Eye movement abnormalities are quite common in MS. These can take many forms depending on the nature of the neurological damage. They might involve rapid but regular eye movements (usually described as
‘nystagmus’) or take a range of other forms including a temporarily fixed gaze. Many of these abnormal movements may not even be recognized by the person with MS, and are more likely to be noticed by others. Occasionally people with MS experience a more troubling form of nystagmus, which involves very slow but regular eye movements associated sometimes with dizziness and nausea. Nystagmus is a difficult condition to treat successfully, for the damage that causes it can be very different in different cases. Clonazepam (Rivotril) can sometimes help the problem, as can baclofen or gabapentin and scopolamine, although it is often a case of trial and error in their use.

Uhtoff ’s phenomenon

Another occasional symptom is a visual disturbance after exercise, a meal or hot bath (‘Uhtoff ’s phenomenon’), almost certainly due to increased body heat affecting nerve conduction. Such a visual disturbance will normally disappear as body heat falls.

Other sight problems

Although it is unusual for someone with MS to lose their sight completely (even if this is only temporary), many people have episodes during which their sight will become worse. Only one, or both eyes may be affected, and your sight may be disturbed in various ways, including:

• double vision (‘diplopia’)
• a blank field or spot in the middle of your vision (‘scotoma’)
• loss of peripheral vision
• blurring of vision
• problems with colour vision, or certain contrasts, such as an unusual balance between light and shade in the visual field
• pain on eye movement from inflammation of the optic nerve.

Visual disturbances may be especially noticeable at night when light is much less, although there may be the impression in daylight of colours being pale or ‘washed out’. You may feel you need to leave a light on at night to assist your vision in the evening.

Management
These visual symptoms are not, unfortunately, correctable by glasses or contact lenses, because they are caused by nerve damage or inflammation. Although these disturbances can be very disconcerting, they do usually settle down on their own over hours, days or, occasionally, weeks, but there may be some residual loss of vision over time. Probably the most sensible approach is to wait, if you can, for the visual disturbances to correct themselves. You may be able to deal with the double vision temporarily by putting a patch over one eye, but this strategy will slow the natural adaptation of the brain to double vision. Sometimes prisms placed in glasses can help to reduce the effects of double vision by bringing the two images together. High-dose corticosteroids (such as methylprednisolone or dexamethasone) can clear problems earlier, but like other powerful drugs, they can cause side effects. You will need to be aware that visual problems can increase with fatigue, infection, stress, etc., and so managing these issues will help those visual problems.

Cataracts

Cataracts (clouding of the lens of the eye) may occur more frequently in people with MS partly because they are linked with the extensive use of cortisone treatments, which have been relatively commonly used in MS. Cataracts can, however, be surgically removed and this can result in a substantial improvement in vision.