By MedWire Reporters
Viewing tests that detect eye movement can accurately identify patients with schizophrenia, research shows.
Overall, schizophrenic patients had abnormal results on viewing tests that combined pursuit, scene viewing, and steady fixation tasks.
"Indeed, on this test no schizophrenia cases are misclassified as normal," report researcher Philip Benson (University of Aberdeen, UK) and colleagues.
Although abnormal eye movements have been documented in unmedicated psychotic patients, there has been almost no success in identifying marker traits associated with schizophrenia that can separate cases from healthy controls.
In the present study, published in Biological Psychiatry, 88 schizophrenia patients were presented with visual stimuli. Smooth pursuit involved tracking a circular target as it moved around the display screen. The ability to scan scenes of everyday objects and fixate on specific images was also assessed.
The free-viewing scanpaths were abnormally restricted in schizophrenic patients, report the researchers, and this was the single biggest discriminator of cases from healthy controls.
They also observed that these patients had impaired scores on the fixation-stability test. This test is a measure of saccade inhibition and can be used to "interpret aberrant patterns in picture viewing, saccade, and pursuit tasks," explain Benson and colleagues.
Additionally, horizontal and "Lissajous" pursuit of the moving images was abnormal compared with controls.
The differential effects were stable over time, and independent of gender, medication usage, and cigarette smoking.
In terms of the predictive validity of the eye-movement tests, re-test assessments and testing on patients with newly diagnosed schizophrenia showed the viewing test predicted schizophrenia in 87.8% of patients. Use of a probability model showed the test could achieve 98% discrimination between schizophrenics and control cases.
"This is a remarkable level of discrimination and well beyond that of other potential trait markers previously reported in schizophrenia," state the researchers.
Other benefits of the eye-viewing test include its low cost, ease of use, and that it can be used in the hospital or clinic on nearly all schizophrenic patients.
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