Researchers reveal impairment of binocular depth perception in schizophrenia

Researchers have demonstrated an impairment of binocular depth perception among patients with schizophrenia confirming early visual processing deficits and reflecting a possible magnocellular deficit.Schizophrenia is associated with a number of sensory and cognitive impairments. Despite early reports of visual deficits in people with schizophrenia, only a limited amount of research has been conducted in this area. Schechter et al. investigated the integrity of binocular depth perception (stereopsis) in patients with schizophrenia.Stereopsis was assessed using the Graded Circles Stereo Test in 17 patients with schizophrenia (clinical and DSM-IV diagnosis) and 19 health volunteers as controls. Only participants with corrected vision of at least 20/32, with no history of visual or ocular pathology, and those with less than one line disparity between eyes on the Early Treatment of Diabetic Retinopathy Study (ETDRS) acuity chart were included into the study.The results revealed patients with schizophrenia to have a marked deficit in binocular depth perception. Stereoacuity for patients on the Graded Circles Stereo Test was significantly elevated compared with controls (mean of 142 arcseconds versus 55 arcseconds, respectively; p=0.006). Furthermore, the percentage of patients with schizophrenia with correct stereopsis detection was significantly reduced at 200, 140, 60 and 50 arcseconds compared with controls (p=0.003).The authors pointed out that their finding "further reinforces the theory that patients with schizophrenia have difficulty in integrating sensory information and constructing unitary percepts from complex visual information."Furthermore, the authors noted that the lack of stereoscopic vision in patients with schizophrenia may be a significant contributor to the dyspraxia that is frequently associated with this condition, and asserted that their current findings reflect a possible magnocellular deficit among patients with schizophrenia. "It remains to be determined; however, whether if the present deficits relate to previously demonstrated magnocellular/parvocellular dysfunction or whether they reflect local dysfunction only within stereoscopic visual areas such as V3A," they concluded.Reference...