Nystagmus is a type of involuntary movement of the eyes. The movement varies between slow and fast and usually involves both eyes.

Different types of nystagmus are:

  • Horizontal—side-to-side
  • Vertical—up and down
  • Rotatory—circular
  • Infantile—tends to develop between 6 weeks and 3 months of age
  • Acquired—occurs later in life

The direct cause of nystagmus is instability in the motor system that controls the eyes. In some cases, the cause of nystagmus is unknown.