New Eye Tracking Technology Promising As Biomarker For Brain Injury And Function
Robert Glatter, MD
Using a new technology which tracks eye movements of patients viewing music videos just under four minutes, researchers at NYU Langone Medical Center have developed a new way to assess the location and impact of a brain injury.
The research was published Dec 16 in the Journal of Neurosurgery.
The research offers promise that such eye tracking technology may serve as a biological marker for evaluating brain function and monitoring recovery for patients who sustain traumatic brain injuries (TBI), with the hope of extending this to evaluation of mild traumatic brain injury (mTBI), commonly referred to as concussions.
For the study, researchers evaluated 169 patients. 157 were neurologically normal, while 12 demonstrated specific abnormalities in cranial nerves controlling eye movement or brain swelling close to those nerves. These nerves affect eye movement sideways as well as up and down.
For the study, researchers, employing a new technology developed at NYU Langone, had participants watch a music video or television content for 220 seconds while they measured the ratio of horizontal to vertical eye movements. In the neurologically normal participants, the ratios were nearly to1:1, with horizontal movements essentially equaling vertical movements. However, the 12 participants with nerve damage or swelling in the brain pressing on nerves demonstrated abnormal eye movement ratios reflecting the affected nerve of interest. In each patient where the abnormal eye movement was secondary to swelling in the brain, surgery to repair the brain abnormality also corrected the eye movements to a normal range.
“We are very excited about the findings because it offers a proof of concept that this technology can detect brain injury and suggest its location,” said Uzma Samadani, MD, PhD, chief of neurosurgery at New York Harbor Health Care System and co-director of the Steven & Alexandra Cohen Veterans Center for the Study of Post-Traumatic Stress and Traumatic Brain Injury at NYU Langone.
“One of the reasons that clinical trials for treatment of brain injury have failed in the past is that brain injury is hard to classify and quantitate with existing technologies. This invention suggests a potential new method for classifying and quantitating the extent of injury. Once validated, it will both accelerate diagnosis and aid in the development of better treatments,” added Samadani.
“These results are extremely exciting because the technology is not overly complicated and, as a result, can move from the bench to the battlefield and other places where it will be easily accessible to all,” explained Dr. Charles Marmar, the Lucius Littauer Professor and Chairman of Psychiatry at NYU Langone, and executive director of NYU Langone’s Steven & Alexandra Cohen Veterans Center, which provided funding for the research.
Marmar feels that the technology is quite user friendly, it can be applied, for example, to study hundreds of subjects in a relatively short period of time. He describes recent eye-tracking studies by Samadani in over 600 active military at Fort Campbell in Kentucky, utilizing this technology one week after returning from deployment, adding “These studies will help further evaluate the technology’s effectiveness as a screening tool.”
TBI affects up to 1.4 million people annually in the U.S., with nearly 50,000 deaths and 235,000 hospital admissions. TBI is the number one cause of death and disability in Americans under age 35, according to the CDC.
Although Samadani’s research evaluated patients with clinical deficits from abnormal neuroimaging studies, she believes the technology will likely be most helpful for the assessment of mild TBI or concussion, as well as those suffering blast-type injuries. Patients with these types of injuries may have minimal findings on CT scans or MRIs—and have typically made up a large percentage of injuries seen in returning veterans from the long Middle East wars.
“Because eye tracking measures how well the brain functions rather than assesses what it looks like, it provides very different information than imaging studies,” added Samandani.
The technology offers potential utility in the triage and evaluation of persons with TBI as well as concussions, according to Samandani.
“When a person falls and hits their head, it can be difficult to determine whether the injury is life-threatening,” explained Samadani . “Eye tracking is potentially a simple, non-invasive and cost-effective way to determine quickly which patients need immediate attention.”
Technology such as this could also be used by first responders and medical providers in emergency departments at triage to evaluate persons after head injuries, and could prompt the need for further need for neuroimaging in the setting of head trauma. Eye tracking evaluation as described in her study may also offer additional clues beyond what a standard physical examination in a busy emergency department could provide, helping medical providers spot early signs of concussion prompting expedited evaluation and referral.
Its use could also be extended to sports venues after athletes suffer what may be a concussion. Evaluation with a simple non-invasive screening test evaluating eye movements may prompt a more detailed neurologic examination of persons with equivocal symptoms or suspected concussion.
Current tests to identify early signs of concussion (abnormalities in balance) such as the balance error scoring system (BESS) can be problematic to perform if a patient has difficulty standing or has a suspected cervical spine injury. (This would require clearance using neuroimaging prior to using BESS.)
Other current screening methods to evaluate for concussion involve rapid number naming aloud (King-Devick) which provides indirect information about visual tracking and saccadic eye movements. Multiple research papers have suggested that abnormalities in saccadic eye movements can be an early marker for concussion.
Samadani’s work is important because it demonstrates the utility of eye tracking technology to assess abnormal physiology in the central nervous system. This technology could potentially serve as a proxy for physical examination, and may offer alternative ways to assess patients remotely (telemedicine) after traumatic brain injury as well as suspected concussions.
Of note, Samadani is co-founder of Oculogica, a neurodiagnostic company specializing in detecting concussions and other brain injuries not evaluated with standard neuroimaging.