Nystagmus refers to rapid involuntary
movements of the eyes that may be from side to side (horizontal
nystagmus), up and down (vertical nystagmus) or rotary. Depending on the
cause, these movements may be in both eyes together or in just one eye.
The term "dancing eyes" has been used in regional dialect to
The abnormal eye movements of nystagmus
are caused by abnormalities of function in the areas of the brain that
controls eye movements, but the exact nature of these disorders is often
poorly understood. Nystagmus may be either congenital (present at birth)
or may be caused by disease or injury later in life.
Congenital nystagmus is the most common.
It 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 amplitude, 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 this.
A less common cause of nystagmus is
disease or injury of the central nervous system.
In young people the most common cause of
acquired nystagmus is head injury from motor vehicle accidents. In older
people the most common 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
Because control of eye movements is
affected by input from the labyrinth (the part of the inner ear that
senses movement and position), inner ear disorders (such as Meniere’s
disease) can also lead to acquired nystagmus. Other causes include
Dilantin (an antiseizure medication), toxicity, and alcohol
Nystagmus may be observed through the
following procedure. If the affected person spins around for about 30
seconds, stops, and tries to fixate on (stare at) an object, the eyes
will first move slowly in one direction, then move rapidly in the
opposite direction. The orientation of these alternating movements (side
to side, up and down, or in a circular pattern) depends on the type of