Nystagmus is a repetitive oscillation of the eyes that is usually rhythmic. Generally, nystagmus is considered as either jerk or pendular. Jerk nystagmus refers to rhythmic back and forth movements in which there is a fast and a slow phase. By convention, nystagmus is described by the direction of the fast phase. Pendular nystagmus refers to rhythmic back and forth movements of the eyes in which the velocity is equal in each direction. The nystagmus may be a mixed combination of both jerk and pendular. This chapter is a clinical-based approach to nystagmus and other texts should be consulted for a detailed pathophysiologic understanding of nystagmus.

Nystagmus may cause visual blurring, but usually does not produce other clinical symptoms or signs. Table 11-1 is a list of the clinical characteristics of congenital nystagmus that allow its differentiation from acquired nystagmus. Table 11-2 lists specific forms of nystagmus that can be localized to particular portions of the central nervous system. Table 11-3 lists those eye movements that can be confused with nystagmus.

Several questions can be asked to better determine the nature of the nystagmus.