Abstract
Binocular depth perception (BDP) is one of the most demanding visual function that involves both dorsal and ventral visual information streams. Substantial research has been conducted on the disruption of BDP in patients with schizophrenia. However, research on first-episode and drug-naive patients with schizophrenia (FEDN) is limited. To assess the BDP of schizophrenia patients while controlling for the effects of antipsychotics and the duration of illness. We investigated BDP in patients with schizophrenia via the Titmus Stereopsis Test in this study, by matching the patients into three groups: FEDN (n = 17), long duration of illness and medicine treatment (LDMT) (n = 31) and the healthy control group (n = 40). Results showed that both the FEDN (mean = 1.71, 95% confidence interval [CI]: [1.57, 1.84]) and LDMT (1.73, 95% CI: [1.66, 1.81]) patients displayed a significant decline (p = 0.01, Cohen’s d = 0.67, p = 0.001, Cohen’s d = 0.92, respectively) in depth perception compared to the healthy control (1.55, 95% CI: [1.48, 1.61]) group. Additionally, there were no significant differences (p = 0.68, Cohen’s d = 0.11) between the FEDN and LDMT groups, and no correlation (Pearson r = -0.16, p = 0.38, R2 = 0.03) was observed between the duration of illness and impaired BDP in the LDMT group. The proportion of individuals with stereopsis detection in either FEDN (12/17) or LDMT (26/31) groups under stereo threshold 63 arc seconds (″), were significantly lower (Pearson χ2 = 6.29, p = 0.043, φc = 0.27) compared to the healthy control group (38/40). Significant difference in stereopsis detection also occurred at 50″ (Pearson χ2 = 12.31, p = 0.001, φc = 0.37), 40″ (Pearson χ2 = 12.38, p = 0.002, φc = 0.38), 32″ (Pearson χ2 = 6.69, p = 0.035, φc = 0.28), 25″ (Pearson χ2 = 14.82, p = 0.001, φc = 0.41) and 20″ (Pearson χ2 = 6.73, p = 0.034, φc = 0.28) between the three groups. These findings showed a moderately strong association between schizophrenia and defective stereopsis.
Highlights
Patients with schizophrenia is associated with a widespread deficiency in cognitive coordination
The dysfunctional Binocular depth perception (BDP) was found in schizotypal personality traits (SPT) (Barbato et al, 2012) and individuals at clinical high risk (CHR) of developing psychosis (Lee et al, 2012), the dysfunction was less severe compared to patients with schizophrenia
There were no statistical outliers within the stereo thresholds of the first-episode and drug-naive patients with schizophrenia (FEDN) and long duration of illness and medicine treatment (LDMT) groups according to the mean ± 3σ criterion, while there was one value (160 ) that was extremely high in the healthy control group
Summary
Patients with schizophrenia is associated with a widespread deficiency in cognitive coordination. A previous study showed that young subjects with clinically high risk of developing schizophrenia (CHR) had normal stereopsis compared with healthy controls. Previous studies found that there is no association between impaired depth perception in patients with schizophrenia and positive and/or negative symptoms or antipsychotic medications (Schechter et al, 2006; Kantrowitz et al, 2009). These findings implied that stereopsis dysfunction might be steady in a different state of schizophrenia. Our findings would add further weight to the proposal that BDP deficits might be involved in the spectrum of neurological changes and that impaired BDP was associated with patients with schizophrenia
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