Quantitative measurement of smooth pursuit eye movements.

Smooth pursuit eye movements were quantitatively assessed in 25 normal subjects and 22 patients. A laboratory digital computer was used to compute 200 eye velocity samples per second and to statistically compare these eye velocity measurements for five different object velocities. Of six statistics evaluated, mode eye velocity showed the least variability in normal subjects and was most frequently abnormal in patients. Compared to normal subjects, patients with brain stem degeneration and cerebellar-pontine angle tumors with brain stem compression had significant impairment of smooth pursuit. Patients with peripheral vestibular lesions and C-P angle tumors without brain stem compression did not have impaired smooth pursuit. These preliminary findings suggest that quantitative measurement of pursuit eye velocity can be a sensitive test for brain stem dysfunction.