Nystagmus is an uncontrolable movement of the eyes that is present from birth or acquired later in life. It can reduce vision and often it is often associated with other more serious eye disorders.
'Congenital nystagmus' (CN) and latent/manifest latent nystagmus (LMLN) are the most common types. Those with CN are often partially sighted, legally blind, and unable to drive a car. Most also have problems in everyday life, both practical and social, to the point they have trouble obtaining education and employment.
However, CN or LMLN by themselves do not necessarily cause major vision problems, and many people with these disorders lead normal, active lives. Those with very poor vision usually have sensory deficits that are responsible for most of their vision loss.
Adult onset acquired nystagmus takes many different forms. Some of the symptoms include oscillopsia, meaning the involuntary movement of the eye, poor vision, and loss of balance. Some acquired nystagmus is caused by neurological problems, and can be treated with medication. Visual field problems are caused by strabismus (misalignment of the eyes), which causes problems with depth perception, clumsiness, tripping, and poor eye-hand coordination.
Nyastagmus can be hereditary, have no known cause, or be associated with a sensory problem. The underlying cause is an instability in the motor system controlling the eyes. CN rarely presents later in life, and acquired nyastagmus can be caused by an accident or a range of illnesses.
These observations are from the American Nystagmus Nework:
Glasses or contact lenses do not correct nystagmus.
Vision may vary during the day and is likely to be affected by emotional and physical factors such as stress, tiredness, nervousness or unfamiliar surroundings.
Most people with CN and no other visual problems can see well enough to drive a car.
The angle of vision is important. Most individuals with CN have a null point (a gaze angle where the CN damps); this point can be found and used by looking to one side or the other, 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 their vision. Sitting to one side of a screen, blackboard, etc. does not help because it reduces the angle at which the screen is viewed, causing 'crowding'. A better solution is to sit directly in front and adopt the preferred head turn or have corrective surgery (or use prisms) to eliminate the head turn.
Many can read very small print if it is close enough or with use of a visual aid. However, the option of large print material should be available and all written matter should be clear. It is very hard to share a book with someone because it will probably be too far away or at the wrong angle.
Good lighting is important. If in doubt get the advice of a specialist, particularly as some people are also light sensitive. Computers are used by many people with nystagmus, who benefit from them as they can position screens to suit their own needs and adjust brightness, character size etc. However some find it difficult to read computer screens. Reading speed is not usually reduced by nystagmus itself, but by other associated visual deficits. CN should not be taken as a predictor of poor reading.
Balance can be a problem in acquired nystagmus, which can make it difficult to go up and down stairs.
This is another condition I hadn't heard of before researching the causes of low vision.
Dale L. Edwards
