Eye movement as a biomarker of schizophrenia: Using an integrated eye movement score.

AIM: Studies have shown that eye movement abnormalities are possible neurophysiological biomarkers for schizophrenia. The aim of this study was to investigate the utility of eye movement abnormalities in identifying patients with schizophrenia from healthy controls.

METHODS: Eighty-five patients with schizophrenia and 252 healthy controls participated in this study. Eye movement measures were collected from free viewing, fixation stability, and smooth pursuit tests. In an objective and stepwise method, eye movement measures were extracted to create an integrated eye movement score.

RESULTS: The discriminant analysis resulted in three eye movement measures; the scanpath length during the free viewing test, the horizontal position gain during the fast Lissajous paradigm of the smooth pursuit test, and the duration of fixations during the far distractor paradigm of the fixation stability test. An integrated score using these variables can distinguish patients with schizophrenia from healthy controls with 82% accuracy. The integrated score was correlated with Wechsler Adult Intelligence Scale-Third Edition full scale IQ, Positive and Negative Syndrome Scale scores, and chlorpromazine equivalents, with different correlation patterns in the three eye movement measures used. The discriminant analysis in subgroups matched for age, sex, years of education, and premorbid IQ revealed a sustained classification rate.

CONCLUSION: We established an integrated eye movement score with high classification accuracy between patients with schizophrenia and healthy controls, although there was a significant effect of medication. This study provides further evidence of the utility of eye movement abnormalities in schizophrenia pathology and treatment.