Impaired eye movements have long been associated with schizophrenia. In a new study, researchers have discovered they can distinguish people with and without schizophrenia through the use of simple eye movement tests with over 98 percent accuracy.

“It has been known for over a hundred years that individuals with psychotic illnesses have a variety of eye movement abnormalities, but until our study, using a novel battery of tests, no one thought the abnormalities were sensitive enough to be used as potential clinical diagnostic biomarkers,” say Dr. Philip Benson and Dr. David St. Clair, lead authors on the paper.

The series of tests included smooth pursuit, free-viewing, and gaze fixation tasks.

In smooth pursuit, people with schizophrenia have difficulty following slow-moving objects smoothly with their eyes. Their eye movements tend to fall behind the moving object and then catch-up with the moving object using a rapid eye movement, called a saccade.

In the free-viewing test — in which a picture is shown — those with schizophrenia follow an abnormal pattern as they look at the picture, compared to the general population.

In the fixation task, the individual is asked to keep a steady gaze on a single unmoving target, which tends to be difficult for individuals with schizophrenia.

In each of the eye tests, the performance of individuals with schizophrenia was abnormal compared to the healthy volunteer group. The researchers then used several methods to model the data. Combining all the data, one of the models achieved 98.3% accuracy.

“We now have exciting unpublished data showing that patterns of eye movement abnormalities are specific to different psychiatric subgroups, another key requirement for diagnostic biomarkers.

“The next thing we want to know is when the abnormalities are first detectable and can they be used as disease markers for early intervention studies in major mental illness,” say the researchers.

“We are also keen to explore how best our findings can be developed for use in routine clinical practice,” they add.

Typical neuropsychological assessments are time-consuming, expensive, and require highly trained individuals to administer, while these eye tests are simple, cheap, and take only minutes to conduct.

A predictive model with such accuracy could potentially be used in clinics and hospitals to aid doctors by supplementing other symptom-based diagnostic criteria.

Source: Biological Psychiatry