Ask the patient to look back and forth between two outstretched fingers held about 12 inches apart in the horizontal and vertical plane. Observe for latency of onset, speed, accuracy, and conjugate movement.
Delayed: Cortical and brain stem lesions
Inaccurate: lesions in cerebellar vermis and fastigial nuclei
Disconjugate with slowing of adducting eye and overshoot of abducting eye implies medial longitudinal fasciculus pathology associated with MS