Binocular depth inversion illusion for early assessment of altered visual information processing in the course of schizophrenia

The Binocular Depth Inversion Illusion Test (BDII) represents a sensitive measure of impaired visual information processing that manifests in various experimental and naturally occurring psychotic states. This study explores impairment of visual processing in different major psychiatric disorders investigating 313 subjects, suffering of either a prodromal state of psychosis (IPS, n=22), first-episode antipsychotic-naïve schizophrenia (SZ-N, n=75), antipsychotically treated schizophrenia (SZ-T, n=74), major depression (MDD, n=35), bipolar disorder (BD, n=20), dementia (D, n=6), and healthy controls (HC, n=81). Patients suffering from either IPS, SZ-N or SZ-T showed significantly higher BDII scores compared to HC, while this was not seen for MDD, BD or D. The potential value of BDII in facilitating prediction of psychoses was assessed using the receiver operating characteristic (ROC) and the area under curve (AUC). Testing IPS against controls and non-schizophrenic disorders revealed an AUC of 0.700, while testing SZ-N revealed an AUC of 0.692. Our data indicate that visual processing is already disturbed at an early state of schizophrenia-spectrum diseases like IPS and SZ-N. With the current identification of individuals at high risk for psychosis (IPS) relying on psychopathological rating sscales, the BDII may be useful as an additional neuropsychological test for assessment of patients at high risk for developing schizophrenia and its first-break episodes.