New Study on Eye Tracking and Visual Attention and Relationship to Schizophrenia

by Jenna Ward

BERKELEY, February 29, 1997- For nearly one hundred years, doctors have known there was something different about the eyes of many people with schizophrenia - and the eyes of their family members too. The anomaly involves a function called eye tracking, and a new study reported on February 15 in the Archives of General Psychiatry takes a closer look at the phenomenon in first degree relatives of people with schizophrenia.

Eye tracking is the ability to follow a moving target with the eyes. Eight percent of the general population is unable to do this in a smooth motion, compared to somewhere between 50 and 85 percent of schizophrenic patients and about 45 percent of their parents and siblings. This gives eye tracking a clear genetic implication in the study of schizophrenia. Instead of tracking smoothly, "the eye repeatedly falls back and then catches up with jerky movements of the type known as saccadic. The underlying problem may be an ability to perform the functions of the frontal lobe," according to the July, 1995, Harvard Mental Health Letter.

This recent study looked at 83 first-degree relatives of 38 patients with schizophrenia, plus 45 control subjects. They all underwent a clinical evaluation, an eye tracking evaluation, and a Continuous Performance Test (CPT). The CPT measures visual attention - subjects are told to watch a sequence of flashing letters and press a button when, for example, they see an x followed by a p. The researchers began the study with the idea that in addition to eye tracking, relatives of people with schizophrenia are more likely to have problems with the CPT test, as well as demonstrate more schizotypal personality symptoms. Eye tracking proved to be the most powerful way to differentiate the relatives from the control subjects. The researchers did not find any significant correlation between eye tracking scores and mistakes on the CPT test or the presence of schizotypal symptoms. However, people who made mistakes on the CPT were more likely to have schizotypal symptoms. The conclusion - Eye tracking deficits and disturbances in visual attention (i.e. mistakes on the CPT test) are probably two separate things and should be considered independent factors in genetic studies of schizophrenia.



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