Patients’ eyes have long provided important clues to mental health clinicians. Enlarged pupils may be a sign of substance use, for example, and a distant stare might indicate dissociation in response to a certain topic broached in therapy.
Researchers are now investigating more sophisticated methods of gleaning clinical information from the eyes, and the results are showing promise for eventual application in aiding diagnosis and informing treatment.
One such method involves using an eye-tracking device to monitor the duration of a patient’s gaze when presented with emotionally evocative stimuli, such as photos of happy or sad faces. A study published last August in Psychiatry Research found that depressed patients maintained their gaze on happy faces for a shorter amount of time than healthy controls and patients with remitted depression.
According to the researchers, these findings are in line with previous studies suggesting that people with depression tend to have an attentional bias for negative information, which may be one factor that increases vulnerability to depressive episodes.1
Another study, published last March in the same journal, found a similar pattern among patients in the depressive phase of bipolar disorder: They paid less attention to happy faces as compared to healthy controls.2
A study in the August 2014 issue of Vision Research focused on involuntary eye movement as a potential marker of attention-deficit/hyperactivity disorder (ADHD). Researchers compared the rate of eye blinks and microsaccades (small, rapid movements of the eyes as they shift attention from one point to another) among 22 patients with ADHD and 22 healthy control subjects as they performed the Test of Variables of Attention (TOVA).
Each group performed the test twice in one day. The ADHD group completed the first test while they were unmedicated, and they performed the second test after taking their medication. The ADHD patients had significantly higher rates of blinks and microsaccades than controls, especially around the time that the stimulus appeared. These rates approached or reached normal levels, however, when the patients took the test while medicated.3
One of the study’s authors, Moshe Fried, PhD, of Tel Aviv University, explained that visual attention can be allocated spatially (to a specific location in the visual field) or temporally (to a time interval when the individual anticipates that a visual stimulus will be shown). He and his colleagues focused on temporal allocation in their study.
“As microsaccades and blinks interfere with visual stimulus acquisition, both are normally suppressed while anticipating visual stimuli,” Fried said. Indeed, they found that this suppression was significantly stronger in control subjects versus patients with ADHD.
“We interpreted our results as the failure of ADHD subjects to maintain the level of arousal in simple and prolonged tasks, thus resulting in impaired ability to dynamically allocate attention during anticipation of the visual stimulus.”