| nystagmus | <neurology> An involuntary, rapid, rhythmic movement of the eyeball, which may be horizontal, vertical, rotatory or mixed, i.e., of two varieties. Origin: Gr. Nystagmos = drowsiness, from nystazein = to nod (18 Nov 1997) |
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| nystagmus, optokinetic | The normal or physiological nystagmus induced by the attempt to fixate objects moving rapidly across the field of vision. It occurs, for example, when viewing objects from a moving railroad car or automobile. It is also called railroad nystagmus. (12 Dec 1998) |
| nystagmus, physiologic | Involuntary rhythmical movements of the eyes in the normal person. These can be naturally occurring as in end-position (end-point, end-stage, or deviational) nystagmus or induced by the optokinetic drum (nystagmus, optokinetic), caloric test, or a rotating chair. (12 Dec 1998) |
| deviational nystagmus | A jerky, physiologic nystagmus occurring in a normal individual when attempts are made to fixate a point at the limits of the field of fixation. Synonym: deviational nystagmus. (05 Mar 2000) |
| dissociated nystagmus | A nystagmus in which the movements of the two eyes are dissimilar in direction, amplitude, and periodicity. Synonym: dysjunctive nystagmus, incongruent nystagmus, irregular nystagmus. (05 Mar 2000) |
| downbeat nystagmus | A vertical nystagmus with a rapid component downward, occurring in lesions of the lower part of the brainstem or cerebellum. (05 Mar 2000) |
| dysjunctive nystagmus | A nystagmus in which the movements of the two eyes are dissimilar in direction, amplitude, and periodicity. Synonym: dysjunctive nystagmus, incongruent nystagmus, irregular nystagmus. (05 Mar 2000) |
| incongruent nystagmus | A nystagmus in which the movements of the two eyes are dissimilar in direction, amplitude, and periodicity. Synonym: dysjunctive nystagmus, incongruent nystagmus, irregular nystagmus. (05 Mar 2000) |
| irregular nystagmus | A nystagmus in which the movements of the two eyes are dissimilar in direction, amplitude, and periodicity. Synonym: dysjunctive nystagmus, incongruent nystagmus, irregular nystagmus. (05 Mar 2000) |
| ocular nystagmus | The pendular or, rarely, jerky nystagmus seen in severely reduced vision. Synonym: amaurotic nystagmus. (05 Mar 2000) |
| opticokinetic nystagmus | Nystagmus induced by looking at moving visual stimuli. Synonym: opticokinetic nystagmus, railroad nystagmus. (05 Mar 2000) |
| optokinetic nystagmus | Nystagmus induced by looking at moving visual stimuli. Synonym: opticokinetic nystagmus, railroad nystagmus. (05 Mar 2000) |
| end-point nystagmus | A jerky, physiologic nystagmus occurring in a normal individual when attempts are made to fixate a point at the limits of the field of fixation. Synonym: deviational nystagmus. (05 Mar 2000) |
| jerky nystagmus | Nystagmus in which there is a slow drift of the eyes in one direction, followed by a rapid recovery movement, always described in the direction of the recovery movement; it usually arises from labyrinthine or neurologic lesions or stimuli. (05 Mar 2000) |
| upbeat nystagmus | A vertical jerky nystagmus with a rapid component upward, occurring with brainstem lesions. (05 Mar 2000) |