Nystagmus is involuntary movement of the eyes. These eye movements may be slow or fast, steady or jerky, and the eyes may move from side to side or up and down or both.

It is normal for most people to have some degree of nystagmus in response to certain visual patterns. For instance, a person may have mild, temporary nystagmus when driving past a series of telephone poles along the highway.

Abnormal nystagmus may be caused by inner ear problems, certain drugs, alcohol, multiple sclerosis, a brain tumor, or other diseases of the brain and nervous system. Nystagmus can also be present at birth or develop in the first few months of life as a result of problems with visual development.

Treatment for nystagmus usually involves treating the cause, although this is not always possible. Medication can improve some types of nystagmus.