Analysis of slight abnormalities in eye movement may lead to a noninvasive screen for psychiatric disease, according to research findings from the Psychiatry Department at the University of Illinois at Chicago (USA).

Irregularities in how the eyes track a moving object reflect defects in the neural circuitry of the brain and appear to correspond with particular mental disorders. People with schizophrenia, for example, have difficulty keeping their eyes focused on slow-moving objects. With new technology, these abnormalities can be measured precisely and compared with normal patterns.

"Psychiatric illnesses are not well understood neurologically," said Dr. John Sweeney, in whose department the research is being conducted. "Eye movement tests offer a way to investigate abnormalities in the brain that are causing these disturbances."

The goal, Sweeney said, is to develop eye movement tests as a simple, noninvasive tool for diagnosing brain disorders including schizophrenia, depression, and developmental illnesses such as autism. "At present, however, the field is still in its infancy," he noted.

Sweeney and his colleagues are testing eye movement patterns in patients diagnosed with disorders including schizophrenia, bipolar disorder, and depression in order to begin to validate eye movement abnormalities as markers for different diseases.

For these studies, participants undergo a 90-minute series of visual tests in a specially designed laboratory. Seated in a dark room with their heads secured in a chin rest, subjects are shown a pinpoint of light on the opposite wall. They are asked to focus on the light as it jumps from one spot to another, to anticipate the location of the light after it has disappeared and to follow the light as it glides to the left or right at different speeds.

Various tasks are designed to test the function in different parts of the brain controlling cognitive operations and eye movements. One task, for example, tests short-term memory. Subjects are shown a brief flash of light; after a several-second delay, they are asked to move their eyes to the remembered location.

Participants wear infrared spectacles called scleral-reflection glasses, which are linked to a nearby computer that records small movements of the eyes very precisely. The measurements are made using software developed in the investigators’ laboratory. Participants also complete similar tasks in a magnetic resonance imaging scanner, enabling the researchers to observe the corresponding brain activity directly. With the scanner, the brain regions controlling different types of eye movements are systematically investigated one at a time.

Sweeney and his colleagues, who have been studying eye movement patterns for 20 years, are using their laboratory to document impairments associated with disease and injury and to chart the normal course of brain and cognitive development from ages 8 to 15 years. During that period, they say, the brain undergoes important changes affecting eye movement control. Neurodevelopmental disorders can interfere with this maturation.

"Eye movement studies provide a noninvasive way to gain a deeper understanding of the brain dysfunctions at the root of psychiatric illnesses," said Sweeney. "We are following patients over time to monitor the progression of their disease and determine whether different treatments are improving their brain and cognitive function."

"And in the long-term future," he added, "through our efforts to link eye movement and cognitive abnormalities to their underlying genetic causes, we hope to be able to identify high-risk individuals and someday prevent the onset of some of the most common and severe brain disorders that now overwhelm our mental health treatment services."