Quantitative analysis of eye tracking dysfunction (ETD) in first-episode schizophrenia

Eye tracking dysfunction (ETD) is a trait found in a large proportion of schizophrenics and their relatives. ETD may prove useful to genetic researchers as a biological marker for liability to schizophrenia. This study represents an effort to more precisely characterize the nature of ETD. Precise quantitative eye tracking data for 43 first-episode schizophrenics and 42 normal controls who participated in an ongoing longitudinal investigation of the biology of schizophrenia were scored and analyzed using standardized eye tracking data processing procedures and software. 48.8% of the schizophrenics but only 4.8% of the normal subjects had ETD ({dollar}p<.001{dollar}). The eye tracking of schizophrenics with normal tracking was quantitatively indistinguishable from that of normal subjects with normal tracking. Among schizophrenics with ETD, the tracking disturbance appeared to be a function of both smooth pursuit and saccadic system abnormalities ({dollar}p<.05{dollar}). This investigation replicates in a first-episode sample the frequently observed finding that schizophrenia is strongly associated with ETD. The findings suggest a mixed etiology hypothesis of ETD in schizophrenia.