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Richard F. Lewis, Thomas O. Crawford; Slow Target–Directed Eye Movements in Ataxia-Telangiectasia. Invest. Ophthalmol. Vis. Sci. 2002;43(3):686-691.
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purpose. To analyze the slow eye movements that shift the direction of gaze in
patients with ataxia-telangiectasia (A-T).
methods. Eye and head movements were recorded with search coils in three
patients with A-T during attempted gaze shifts, both with the head
immobilized and free to move.
results. Gaze shifts frequently included both saccadic and slow components. The
slow movements were recorded after 42% of saccades and had an average
peak velocity of 6.1 deg/sec and a mean amplitude of 2.0°. They
occurred with the head stationary and moving, could be directed
centripetally or centrifugally, had velocity waveforms that were
relatively linear or exponential, and always moved the eyes toward the
conclusions. The slow movements appear to differ from pursuit and vestibular eye
movements and are not fully explained by the various types of abnormal
eye movements that can follow saccades, such as gaze-evoked nystagmus
or postsaccadic drift. Their origin is uncertain, but they could
represent very slow saccades, due to aberrant inhibition of burst cell
activity during the saccade.
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