Nystagmus is characterised by an involuntary movement of the eyes, which often seriously reduces vision. In the UK many people with nystagmus can register as sight impaired; few can drive a car; most encounter some difficulties in everyday life - both practical and social - and some lose out on education and employment opportunities.
Effects: Early Onset Nystagmus is far more than just poor distance vision. Nystagmus is a dynamic condition, so apart from poor visual acuity (distance vision), it also affects our vision in terms of:
- Time: we need moretime to seethan normally sighted people.
- Distance: you may hear medical people use phrases like ?nystagmus dampens on convergence?. This means that the nystagmus eye movement is reduced the closer we get to the object being viewed. The less the eyes move, the easier and more comfortable it is for us to see.
- Effort: we need to make more effort to see what we do see than a normally sighted person would.
- Direction: often our best vision is in one narrow gaze direction only (the null point or null zone). In all other directions our vision is poorer.
- Movement: we find it hard track moving objects and in some cases may not see very fast moving objects. This includes for example footballs, vehicles, even subtitles on a TV or cinema screen.
- Oscillopsia: although people with early onset nystagmus do not experience the world moving all the time, we can experience this sensation (known as oscillopsia) when we are tired, stressed, anxious, ill or excited. People with acquired nystagmus experience oscillopsia most or all of the time.
- Variability: our vision can change throughout the day and will get worse when tired, stressed, anxious, ill or excited for example.
- Clutter/crowding: it is far harder for us to see in crowded, cluttered or busy places. Examples include busy streets, shops, railway stations, airports, school playgrounds, even busy computer screens.
- Balance: many people with nystagmus report problems with balance.
- Light sensitivity: although there is no known direct link between nystagmus and light sensitivity, many people with nystagmus are sensitive to bright lights, glare and sunshine because of associated conditions. These include albinism, rod/cone dystrophies and high myopia (severe short-sightedness)
Prevalence: Most experts agree that nystagmus affects about one in a thousand people, although some studies suggest it is more common. Different estimates may be due to factors such as the definition of nystagmus and local population variations.
Causes: Nystagmus may be inherited or result from a sensory or neurological problem. Nystagmus often occurs with eye conditions such as childhood cataracts, albinism, optic nerve atrophy, coloboma, etc. In some cases nystagmus occurs for as yet unidentified reasons (idiopathic). It can also develop in later life sometimes as a result of an accident or an illness (e.g. multiple sclerosis or stroke), especially those affecting the motor system, when it is known as acquired nystagmus. You should always consult a doctor if you or a member of your family has nystagmus.
Below are some observations which apply in MOST cases
Glasses or contact lenses do not correct nystagmus, although they should be worn to correct other vision problems. Nystagmus often affects the nerves behind the eye rather than the eye itself.
The angle of vision is important. Many people with nystagmus have a null point (by looking to one side or the other, or up or down) where the eye movement is reduced and vision improved. Those with a null point will often adopt a head posture to make best use of vision. Sitting to one side of a screen, blackboard, etc. often helps.
Small print. Many of us can read very small print if we get close enough or use a visual aid. However, this is physically demanding and tiring, so large print material should be available and all written material should be clear. If you have nystagmus, it is very hard to share a book with someone because it will probably be too far away or at the wrong angle.
Good Lightingis important. If in doubt get specialist advice, particularly as some sufferers are also light sensitive.
Computersare used by many people with nystagmus who can position screens to suit their needs and adjust brightness, character size, etc. However, some find it difficult to read computer screens.
Reading speedmay be reduced by nystagmus because of the extra time needed to scan, but it should not be taken as a sign of poor reading ability.
For more information visit our Shop to see our publications. Early Onset Nystagmus, for instance, answers many questions about nystagmus in greater detail.
Finally, please remember that a widespread lack of understanding of nystagmus is often as much a source of difficulty as nystagmus itself. We are doing our best to overcome this problem and would be glad if you could help us in this aim.