Definition of Nystagmus:

Nystagmus is a term to describe fast, uncontrollable movements of the eyes that may be:

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

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

Considerations:

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.

There are two forms of nystagmus:

• Infantile nystagmus syndrome (INS) is present at birth.
• Acquired nystagmus develops later in life because of a disease or injury.

Common Causes:

NYSTAGMUS THAT IS PRESENT AT BIRTH (infantile mystagmus syndrome, or INS)

INS is usually mild. It does not become more severe, and it is not related to any other disorder.

People with this condition are not aware of the eye movements, but other people may see them. If the movements are large, sharpness of vision (visual acuity) may be less than 20/20. Surgery may improve vision.

Nystagmus may be caused by congenital diseases of the eye. Although this is rare, an ophthalmologist should evaluate any child with nystagmus to check for eye disease.

ACQUIRED NYSTAGMUS

The most common cause of acquired nystagmus is certain drugs or medication. Phenytoin (Dilantin) - an antiseizure medication, excessive alcohol, or any sedating medicine can impair the labyrinth's function.

Other causes include:

• Head injury from motor vehicle accidents
• Inner ear disorders such as labyrinthitis or Meniere's disease
• Stroke
• Thiamine or vitamin B12 deficiency

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