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Nystagmus refers to repetitive, to-and-fro movements of the eyes that are initiated by slow phases. The returning eye movements may be saccades (jerky nystagmus) or slow eye motion (pendular nystagmus). Nystagmus should be differentiated from the saccadic intrusions or oscillations that are initiated by saccades. Physiologic nystagmus may occur during rotational, caloric, and optokinetic stimuli. However, most nystagmus indicates underlying pathology. The clinical examination for pathologic nystagmus should include a systematic study of changes in fixation, eye position, and head position. Head shaking, hyperventilation, vibration, and loud noise may trigger nystagmus. Although nystagmus is often described by the direction of its quick phases, it is the slow phases that reflect the underlying disorder. Differentiating peripheral from central nystagmus is most important in clinical practice. Peripheral nystagmus is mixed torsional- horizontal, beating away from the lesion side. Pure vertical, pure torsional, pure horizontal, and direction-changing nystagmus signify central lesions. Careful observation of nystagmus gives valuable information on the underlying pathology.