Nystagmus is the involuntary movement of the eyes. It is common for all individuals, but some types of nystagmus, such as horizontal nystagmus, can become more severe and pronounced if a driver is intoxicated. Nystagmus types can vary and jerk nystagmus is considered the slow drift of a driver's eyes in one direction with a fast recovery in the other direction. Most individuals who have jerk nystagmus developed it early in childhood from a disease or trauma.