Abstract

INTRODUCTION

Most readers will already know that nystagmus is a to-and-fro movement of the eyes. Because it is a normal as well as an abnormal phenomenon, human beings must have been aware of it for many millennia. However, the first formal description of the oculomotor response to vestibular stimulation is credited to Erasmus Darwin in 1796, and of optokinetic nystagmus to Purkinje in 1819. The term is apparently thought to derive from the jerky head-nodding which occurs when a person drifts off to sleep in the upright position.

Nystagmus can occur in any direction – horizontal, vertical or torsional – and it has several different possible waveforms (Fig. 1). Most doctors should be able to distinguish jerk nystagmus from pendular and complex waveforms, though this can sometimes be difficult. Jerk nystagmus is the most common type: there is a fast saccadic, usually corrective, phase interspersed between slow movements (usually pathological) in the