NYSTAGMUS is characterized by an involuntary movement of the eyes, which may reduce vision or be associated with other, more serious, conditions that limit vision. Nystagmus may be one of several infantile types or may be acquired later in life.
The most common types of infantile nystagmus are 'congenital nystagmus' (CN) and latent/manifest latent nystagmus (LMLN). Many people with CN are also partially sighted; some are registered blind; few of these can drive a car, most encounter some difficulties in everyday life -- both practical and social -- and some lose out on education and employment opportunities. However, CN or LMLN by themselves do not necessarily reduce acuity substantially and many people with these disorders lead normal, active lives. Those with very poor vision usually have associated sensory deficits responsible for the greater part of their vision loss.
There are many types of adult-onset acquired nystagmus. These are often associated with oscillopsia (the experience of the world 'wiggling'), poor vision, and loss of balance. Often acquired nystagmus is a result of neurological problems and may respond to certain drugs, depending on the cause of the nystagmus.
DEPTH OF FIELD VISION is not reduced by nystagmus; it results from strabismus (misalignment of the eyes). Strabismus may sometimes accompany CN and always acccompanies LMLN. Sufferers of strabismus do not develop strong stereoscopic (3-dimensional) vision and may be prone to tripping or clumsiness. Coordination is usually adequate for most tasks, but strabismus sufferers are unlikely to excel at sports needing good hand to eye coordination.
INCIDENCE. Experts agree that congenital nystagmus affects about one in several thousand people. One survey in Oxfordshire, England identified one in every 670 children by the age of two. The flautist James Galway is probably the best known person with congenital nystagmus.
CAUSES. Nystagmus may be inherited, be idiopathic (no known cause), or be associated with a sensory problem; its direct cause is an instability in the motor system controlling the eyes. Rarely, CN can develop in later life; acquired nystagmus may be a result of an accident or a range of illnesses, especially those affecting the motor system. You should always consult a doctor if you or a member of your family has nystagmus.
EFFECTS. Nystagmus affects different people in different ways. While there are general patterns, good advice for one person may be inappropriate or even bad for another, especially where other eye problems are present.
Below are some observations which apply in MOST cases:
Grateful acknowledgement is made to the Nystagmus Network (U.K.) for permission to use this text, with minor revisions.