Depending on the cause, these movements may be in both eyes together or in just one eye. 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.
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. 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.