Abstract
Patients with psychotic disorders are found to have deficits in pursuit eye movements. However, the ocular motility of some of these patients is within the normative range (Nkam et al., 2010). The aim of the present study was to evaluate smooth pursuit eye movements in schizophrenia and bipolar disorders patients and analyze the association with severity of symptoms and executive functions. Participants were thirty-seven patients with schizophrenia, fifty-eight with bipolar disorder (age range 18–55 years) and twenty-two age-matched controls. The patients were recruited from a psychiatric hospital and diagnosed according to DSM-V criteria. Symptoms severity was measured using the Brief Psychiatric Rating Scale (BPRS). Executive functions were assessed with Wisconsin Card Sorting Test (WCST). Smooth pursuit eye movements were recorded using the Eye Tribe infrared system and elicited using computer-based stimuli. The gain and the latency were used to measure the pursuit efficiency. The gain was calculated as the ratio of eye velocity to target velocity. The latency was calculated as the difference between the phase of the eye fitting curve and that of the stimulus fitting curve. From the generalized linear model, both schizophrenic and bipolar disorder patients showed significantly impaired smooth pursuit with higher latency and lower gain as compared to controls, indicating a general difficulty in following a moving target. No differences were found between schizophrenic and bipolar disorder patients for gain and latency. Moreover, the ocular motility deficit was correlated with WCST score and not with BPRS score, confirming that the patients’ efficiency in smooth pursuit was linked to executive functions and not merely to symptoms severity. These findings are in accordance with previous studies and they specify that the deficit in pursuit eye movements in psychotic patients is associated with impairment in executive functions.