Nystagmus is a common sign in diseases of the nervous system, and it is also observed in diseases of the eye and of the inner ear. It may, however, be a normal phenomenon in certain circumstances, or it may be elicited experimentally or as part of the clinical examination. There are many varieties of nystagmus, and the manifestation should not be considered as an entity. In order to evaluate the significance of the presence of nystagmus in any individual instance, one must understand the underlying mechanisms and the mode of production of the phenomenon.
Nystagmus, or, as it is sometimes called, talantropia,1 may be defined as an involuntary oscillation or trembling of the eyeball. The term "rhythmic" is often included in the definition, but nonrhythmic varieties may be seen. Certain observers object to the inclusion of the adjective "involuntary," as nystagmus of volitional origin has been described. Nystagmus is
DeJONG RN. NYSTAGMUS: AN APPRAISAL AND A CLASSIFICATION. Arch NeurPsych. 1946;55(1):43–56. doi:10.1001/archneurpsyc.1946.02300120053003
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