Nystagmus

Involuntary rhythmic oscillation of the eyes. There are many types. Jerk nystagmus is slower in one direction, with a fast corrective saccade in the other direction. Jerk nystagmus is named for the direction of the fast phase, e.g., left-beating, downbeating. Examples of jerk nystagmus are:

1) Downbeat nystagmus does not mean any downbeating nystagmus, but only downbeating nystagmus that occurs spontaneously in the primary gaze position.

2) Gaze-evoked nystagmus occurs only with eccentric gaze, with the fast phase occurring in the direction of gaze.

Revised, June 1, 2010