Keefe et al1 recently reported the interesting finding that qualitative ratings of smooth pursuit eye movements were more powerful than quantitative measures in discriminating relatives of patients with schizophrenia from control subjects. Their quantitative measures included gain and frequency of small and large saccades. They remarked that "qualitative and quantitative measures of eye tracking may reflect independent dimensions of disturbance."1(p175) We attempted to test this idea by examining the relationship between qualitative and quantitative measures of eye tracking in a sample of schizophrenic patients.
Ross DE, Thaker GK, Buchanan RW, Lahti AC, Conley R, Medoff D. Specific Measures Account for Most of the Variance in Qualitative Ratings of Smooth Pursuit Eye Movements in Schizophrenia. Arch Gen Psychiatry. 1998;55(2):184-185. doi: