Smooth pursuit eye movements in chronic schizophrenics and healthy volunteers using a quantitative objective measure for detecting saccadic intrusions

Abstract

An electro‐oculogram based eye tracking system (the Cardiff System for the Generation and Analysis of Saccades) was used to quantify smooth pursuit eye movements (SPEM) and saccadic intrusions in 20 chronic schizophrenic patients and 16 normal, healthy controls. Statistically significant differences were found between the two groups at all four target frequencies tested (0·2, 0·25, 0·33 and 0·5 Hz) in three measures of SPEM dysfunction (position error, velocity error and saccadic intrusions). Of the patients' position errors, 50–70 per cent were greater than the 95th percentile for controls. Velocity errors gave a similar range of SPEM dysfunction (50–65 per cent) but the frequency of saccadic intrusion abnormality was more variable (20–60 per cent). Position error and saccadic intrusions, at the fastest target speed, correlated with total BPRS scores. Extrapyramidal symptoms (Simpson and Angus) and abnormal involuntary movements also correlated with saccadic intrusions at 0·5 Hz. There were no significant correlations between SPEM dysfunction and age, duration of illness, negative symptoms (total SANS score) or current dose of antipsychotic drug treatment. Copyright © 1999 John Wiley & Sons, Ltd.