Eye Tracking Test May Detect Concussion

Laird Harrison

March 05, 2015

An eye tracking test may detect and help quantify the disruption of ocular motility associated with concussion, a new study shows.

Researchers report that the test, a novel eye tracking device, distinguished patients with concussion from healthy controls or those with nonhead injuries. The degree of disruption in eye movements detected by the device also correlated with the severity of the injury.

The technique is a sensitive, objective method for separating concussions from other conditions, lead author Uzma Samadani, MD, PhD, told Medscape Medical News.

"I hope that we change the way concussion is diagnosed and defined," she said.

Dr Samadani, co-director, Steven and Alexandra Cohen Veterans Center for PTSD and TBI in New York, New York, and her colleagues published the study online in the Journal of Neurotrauma. Dr Samadani reported that she has financial interest in Oculogica, a company she cofounded to market the technology used in this study, called Eyebox.

Not a New Idea

Using eye movements to detect concussion isn't a new idea. Records of the approach go back to the Edwin Smith papyrus, an ancient Egyptian treatise on trauma surgery. "When I looked at the literature for the oldest known example of abnormal eye movement associated with brain injury, I kept going back and back," said Dr Samadani. "I was in the '50s, '40s and '30s, and suddenly I was in 1500 BCE."

Physicians still often diagnose concussion by watching patients' eye movements while asking them to follow the motion of a finger.

Such methods can work, said Dr Samadani. "I would say they're variable depending on the examiner. If you get a really great ophthalmologist or optometrist, they can detect really subtle differences."

But often practitioners focus on how well subjects can follow a command to move their eyes from one point to another, said Dr Samadani. Someone dazed from an injury may be unable or unwilling to listen to instructions. Children, or someone not speaking the language of the examiner, might also have trouble following the instructions.

For a more objective measure, they have developed a novel eye movement tracking algorithm that follows how the subject's eyes move in conjunction vertically and horizontally over 200 seconds while the subject watches a video.

"We don't care where you look," said Dr Samadani. "We care that your eyes move together over time." For this reason, it could work better in those unable to follow instructions, including animals, said Dr Samadani.

The possibility of diagnosing concussions with this approach first occurred to Dr Samadani when she was studying eye movements in patients in minimally conscious and persistent vegetative states.

"We realized that people who had swelling in their brain were not able to move their eyes in the same way as normal healthy controls," she said. "It became clear to me immediately that this had tremendous implications for concussions."

Current definitions of concussion depend on subjective criteria, and many have been proposed. Dr Samadani believes her team's technique can objectively separate concussion from other types of brain injury. "To me a concussion is radiologically silent brain injury," she said. "If you can see it on CT [computed tomography] scan, it's not a concussion; it's a structural brain injury."

Dr Samadani's team hopes to validate, standardize, and automate eye movement measurements as a means of detecting concussion. They have started a company, Oculogica, to design and sell a portable device that could be used in the emergency department or at the site of an injury, such as the sidelines of a football game.

To test a prototype of the device, she and her colleagues prospectively compared four groups of adults:

  • Healthy controls (n = 64)

  • Patients with head trauma with brain damage visible on CT (n = 13)

  • Patients with head trauma without brain injury visible on CT (n = 39)

  • Patients with trauma that did not involve the head (n = 23)

The researchers found that patients with head trauma were more likely than the healthy persons to have trouble moving their eyes together horizontally in five of five measures, regardless of whether a brain injury showed up on CT. The difference was statistically significant (P < .02).

There was a similar difference between the head trauma patients and the healthy patients on of one of five vertical measures.

In addition, the researchers found that three metrics for horizontal disconjugacy in the all the trauma patients corresponded to clinical signs of concussion as measured by the Sport Concussion Assessment Tool, Third Edition (SCAT3), and the Standardized Assessment of Concussion.

The researchers also tested the participants' balance. They did not find a difference between the patients with head trauma and the trauma patients with other bodily injures.

Only 39 trauma patients returned for follow-up. The abnormal eye movements in these patients improved over time.

Those without brain damage visible on CT reached the same levels as the uninjured controls. But those whose brain damage was visible on CT remained significantly different from the normal controls in four of five horizontal measures more than 4 weeks after their injuries.

"Concussion may be the first of several neurologic disorders for which eye tracking will be the preferred diagnostic," the authors write. "Other candidate disorders include hydrocephalus, intracranial hypertension, normal pressure hydrocephalus and neurodegenerative diseases."

Promising Technology

The new technology "has promise," Christopher Giza, MD, told Medscape Medical News. Dr Giza, who directs the Steve Tisch BrainSPORT concussion program at the University of California, Los Angeles, was not involved in the study.

He agreed with Dr Samadani that the test could provide helpful new objective criteria for diagnosing a concussion.

But he pointed out some limitations to the study. First, its sample size is relatively small, and second, the results were not compared with the more traditional measurements of eye movement in patients with head injury.

"We don't know if their method is picking up stuff that would not have been found," with these more traditional approaches, he said. "It might be that me, examining a patient and having them track my finger all the way to the left and all the way to the right, might pick up something that their test doesn't pick up."

Dr Samadani has submitted patents describing the technology used in this paper. These patents are owned by New York University (NYU) and the Department of Veterans Affairs (VA) and licensed to Oculogica Inc, a company cofounded by Dr Samadani and coinvestigator Robert Ritlop. Dr Samadani's research and the work of statisticians Meng Qian, PhD, and Meng Li, MS, are supported by the Steven and Alexandra Cohen Veterans Center For Post-Traumatic Stress and Traumatic Brain Injury. This work also is sponsored by the NYU Applied Research Support Fund. Dr Samadani's work also is funded by a VA Merit Award and by the National Space and Biomedical Research Institute to evaluate eye tracking as a diagnostic tool for elevated intracranial pressure. Dr Giza has disclosed no relevant financial relationships.

J Neurotrauma. Published online January 12, 2015. Abstract

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