The relationship between visual dysfunction and cognitive deficit in schizophrenia

OBJECTIVE To investigate whether visual processing abnormalities are the result of visual dysfunction involving cognitive impairment or independent abnormalities and to identify the relationship of visual impairments with cognitive functions and severity of psychopathological symptoms. MATERIAL AND METHODS We compared results of visual size perception and actions on objects (motor assessment) in patients with schizophrenia (n=37), including patients with non-resistant schizophrenia (n=19) and healthy individuals (n=20). Cognitive impairments were assessed with BACS. Severity of schizophrenia symptoms was assessed with PANSS. RESULTS The error in the visual size perception test was smaller in healthy controls compared with non-resistant patients (p<0.03). There are no significant differences between non-resistant patients and other groups. Also, there are no significant differences in motor assessment between healthy controls and patients with schizophrenia. In the visual size perception test, the amount of error correlates with cognitive impairments (r= -0.84, p<0.001), and the severity of psychotic symptoms on PANSS (r=0.55, p<0.05). CONCLUSION Changes in visual threshold in patients with schizophrenia are correlated with cognitive dysfunction and reflect dysfunction in the parvocellular system.