Square-Wave Jerks

Square-Wave Jerks

Square-wave jerks are small saccades which interrupt fixation, moving the eye away from the primary position and then returning. This instability of ocular fixation is a disorder of saccadic eye movements in which there is a saccadic interval (of about 200 ms; cf. ocular flutter, opsoclonus). Very frequent square-wave jerks may be termed Square-wave oscillations. Very obvious square-wave jerks (amplitude > 7°) are termed macro-square-wave jerks.
Square-wave jerks are often best appreciated on ophthalmoscopy. Their name derives from the appearance they produce on electro-oculographic recordings.
Although square-wave jerks may be normal in elderly individuals, they may be indicative of disease of the cerebellum or brainstem, e.g., Huntington’s disease, Parkinson’s disease, progressive supranuclear palsy, cerebellar degeneration.

Cross References

Nystagmus; Ocular flutter; Opsoclonus; Saccadic intrusion, Saccadic pursuit