Definition of Nystagmus:

Nystagmus refers to rapid involuntary movements of the eyes that may be:

• Side to side (horizontal nystagmus)
• Up and down (vertical nystagmus)
• Rotary

Depending on the cause, these movements may be in both eyes or in just one eye. The term "dancing eyes" has been used in regional dialect to describe nystagmus.

Considerations:

Uncontrollable eye movements are involuntary, rapid, and repetitive movement of the eyes.

The involuntary eye movements of nystagmus are caused by abnormal function in the areas of the brain that control eye movements. The part of the inner ear that senses movement and position (the labyrinth) helps control eye movements.

The exact nature of these disorders is poorly understood.

There are two forms of nystagmus:

• Congenital nystagmus is present at birth. This is the most common type.
• Acquired nystagmus develops later in life because of a disease or injury.

Common Causes:

CONGENITAL NYSTAGMUS

Congenital nystagmus is usually mild, does not change in severity, and is not associated with any other disorder.

Affected people are not aware of the eye movements, although they may be noticed by a careful observer. If the movements are of large magnitude, visual acuity (sharpness of vision) may be less than 20/20. Surgery may improve visual acuity.

Rarely, nystagmus occurs as a result of congenital diseases of the eye that cause poor vision. Although this is rare, an ophthalmologist should evaluate any child with nystagmus to check for eye disease.

ACQUIRED NYSTAGMUS

Inner ear disorders such as labyrinthitis or Meniere's disease can lead to acquired nystagmus. However, the most common cause is probably toxic -- certain drugs or medication, including Dilantin (an antiseizure medication), alcohol intoxication, or any sedating medicines can harm the labyrinth.

In young people, a common, serious cause of acquired nystagmus is head injury from motor vehicle accidents.

In older people, a common, serious cause is stroke (blood vessel blockage in the brain).

Any disease of the brain (such as multiple sclerosis or brain tumors) can cause nystagmus if the areas controlling eye movements are damaged.