Eye tracking detects subtle responses in comatose patients

In severe cases of traumatic brain injuries, individuals can slip into prolonged states of unconsciousness, commonly known as a coma. Currently, the gold standard for assessing responsiveness in such patients relies on clinical examinations, particularly bedside eye tracking evaluations.

In these assessments, medical professionals observe how patients respond to visual stimuli, focusing on their fixation and visual pursuit of eye movements. However, these evaluations come with their set of limitations. They rely on the examiner’s experience and can result in misclassifications. The decision to withdraw
life-sustaining treatments often depends on whether a patient remains unresponsive for an extended period. Hence, it is vital to define their responsiveness as accurately as possible.

Researchers from the University of Miami Miller School of Medicine and Jackson Memorial Hospital conducted two studies using
Tobii Pro eye tracking glasses to assess comatose patients’ responsiveness and compare the outcomes to standard bedside clinical examinations.

In the first study, comatose patients were exposed to various visual stimuli, including a finger, the examiner’s face, a horizontally moving mirror, and an optokinetic response test. The findings showed that, although clinical examinations identified two out of ten patients as “not tracking” or “uncertain,” the recordings from eye tracking glasses classified them as “tracking”. All patients displaying tracking signs with the eye tracking glasses recovered consciousness during the six-month follow-up.

In the second study, the researchers tested the idea that the type of stimuli to which the comatose patients respond might matter, and the patients might fixate and track more visually immersive stimuli. The comatose patients were shown 30-second videos, and their tracking eye movements were tracked with Tobii Pro eye tracking glasses. The videos consisted of dynamic characters, such as a dancer, a person skateboarding, and Spiderman. Three out of ten comatose patients exhibited tracking signs when their eye movements were closely monitored with eye tracking glasses. However, these patients were mistakenly categorized as “not tracking” during clinical examinations. Compared to the first study, the immersive video classified one additional patient as “tracking,” which was classified as “not tracking” by traditional bedside stimuli shown in the first study.

These studies demonstrated that comatose patients’ eye tracking response can be sensitively detected using eye tracking glasses. Visually immersive videos may be critical to differentiate subtle tracking using eye tracking glasses. The research findings open new avenues for understanding consciousness in comatose patients and highlight the potential of eye tracking as an accurate and sensitive prognostication tool.

Cited publications

Aklepi et al., (2023). Covert Tracking to Immersive Stimuli in Traumatic Brain Injury
Subjects with Disorders of Consciousness. Journal of Neurotrauma.

Alkhachroum et al., (2023). Covert Tracking to Visual Stimuli in Comatose Patients
With Traumatic Brain Injury. Neurology, 101(11), 489–494.