There are few more types of tests that may indicate vulnerability to schizophrenia. It's a measure of eye tracking. Eye tracking is a measure of Smooth-pursuit eye movements, eye movements that are not believed to be under voluntary control. These normally occur when a person tracks a slow moving target such as a pendulum. Tests of patients diagnosed with schizophrenia showed that about 85% od them exhibited abnormal patterns of smooth-pursuit eye tracking movements (Siever & Coursey, 1985). The pic attached illustrates the difference between the typical tracking pattern of a normal control & the pattern typically found in someone with schizophrenia.
About 50% of the close relatives of these patients also showed this deviant pattern. But, in contrast, only 13% of relatives of other types of patients showed abnormal tracking pattern. Eye tracking & other eye movement abnormalities seem to follow a consistent hereditary pattern when families o patients with schizophrenia are studied. However, this genetic link may not be specific schizophrenia or even to the schizophrenic spectrum of disorders, but may indicate poor motor control which is predictive of a variety of disorders. Poor trackers, even among people who haven't received any psychiatric diagnosis, are likely to have interpersonal difficulties & neurological impairment.
Despite the lack of specificity of eye tracking problems to schizophrenia, an abnormal pattern of eye tracking may serve as a marker of vulnerability to schizophrenia in children who are at risk. Like attention problems on the CPT, abnormal eye tracking patterns seem to be a trait measure rather than a measure of a person's clinical state.
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