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December 1983

Saccadic Intrusions in Schizophrenia: Identity With Square-Wave Jerks?

Author Affiliations

Department of Neurology New York University Medical Center New York, NY 10016

Arch Gen Psychiatry. 1983;40(12):1343. doi:10.1001/archpsyc.1983.01790110085014

To the Editor.—  The saccadic intrusions identified by Levin et al in schizophrenic patients (Archives 1982;39: 1125-1130) closely resemble the phenomenon of square-wave jerks (SWJs) previously described in the neuroophthalmologic literature. Squarewave jerks are couplets of conjugate horizontal saccades, approximately 0.5° to 3° in amplitude (up to 10°), that alternately disrupt and correct fixation.1-3 The duration of SWJs averages 200 ms2,3 and they occur with a maximum frequency of approximately 2 HZ.4 Square-wave jerks may be seen during fixation in 24% of normal subjects at a frequency of up to nine per minute; they tend to increase with age, but are not related to fatigue, distraction, or inattention.2 They are considered identical to the saccadic intrusions of nonparalytic strabismus, but cannot be voluntarily suppressed as well.2,3 An increased frequency of SWJs has been observed in a variety of neurologic disorders including cerebellar disease, multiple sclerosis,

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