Pursuit tracking eye movements were analyzed from selected patients with neurological injuries and compared to the responses of 20 normal subjects. The patients/subjects tracked a small spot of light moving sinusoidally in the horizontal plane at a frequency of 0.4 Hz and a peak-to-peak amplitude of 40 degrees. Eye-movement responses were separated into a smooth-pursuit component and a saccadic component. The smooth-pursuit component was analyzed by calculating the gain, phase, and asymmetry.

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... e saccadic component was quantified by calculating the percentage of the total tracking movement contributed by the saccadic system. The patients with smooth-pursuit impairment exhibited a higher percentage of saccadic tracking and a lower smooth pursuit gain compared to the normal subjects. One patient with a unilateral lesion exhibited significant asymmetry in the smooth-pursuit component. In this case, the direction of the asymmetry indicated the side of the lesion.