New Eye Tracking Technology Can Detect Concussions
Robert Glatter, MD
New Study from NYU-Langone Evaluated Patients With Head Trauma In The Emergency Department
Evaluating whether a person has suffered a concussion is not an exact science. Although there are clues related to abnormalities in balance and potential findings from a basic neurologic examination, detecting a concussion is often based on a patient’s subjective findings such as the presence of nausea, headaches, feelings of cloudiness, along with dizziness. In addition, even patients with a documented concussion may not demonstrate such symptoms early on after head trauma.
While imaging studies such as CT or MRI scans may reveal fractures or bleeding in the brain, they cannot diagnose a concussion, which is broadly defined as a complex pathophysiological process induced by biomechanical forces leading to changes in brain function, characterized by changes in orientation, memory as well as balance.
The CDC estimates that close to 2.5 million U.S. emergency department visits were associated with traumatic brain injury in 2010, up nearly 70 percent over the last 10 years. CT scans and MRIs which can evaluate for bleeding, tissue swelling, or skull fractures are not effective tools for diagnosis of concussion. A reliable tool or biomarker to rapidly evaluate for concussion would be highly beneficial for all persons, across all settings in society.
Now researchers from NYU have developed a new approach using novel eye tracking technology that can spot abnormalities in eye movements which may represent the earliest signs of concussion. Additional information obtained from abnormalities of eye movements may also used to quantify the severity of a concussion.
The research was published online January 29 in the Journal of Neurotrauma.
The goal is that such eye tracking technology may represent a rapid, reproducible, and objective diagnostic tool for evaluating persons with possible concussion which can be utilized in the emergency department or even on the sidelines at sporting events.
The study utilized a novel eye-tracking device to effectively measure the severity of concussion or brain injury in patients presenting to emergency departments following head trauma.
“Concussion is a condition that has been plagued by the lack of an objective diagnostic tool which, in turn, has helped drive confusion and fears among those affected and their families,” says lead investigator Uzma Samadani, MD, PhD, assistant professor in the Departments of Neurosurgery, Psychiatry, Neuroscience and Physiology at NYU Langone. “Our new eye-tracking methodology may be the missing piece to help better diagnose concussion severity, enable testing of diagnostics and therapeutics, and help assess recovery, such as when a patient can safely return to work following a head injury.”
Dating back 3,500 years ago, the eyes have been theorized to be a marker for head trauma, often viewed as a “window into the brain.” Identifying those patients who display abnormal or “dysconjugate” eye movements–eyes moving or rotating in opposite directions– may be the initial sign of disrupted neurologic function that can identify a concussion. It is believed that up to 90 percent of patients with concussions or even blast injuries may show signs of ocular abnormalities associated with their eye movements.
Yet, even with advances in optics and neuro-opthalmology, the current or accepted method or tool used clinically to evaluate eye movements is by asking a patient to follow a medical provider’s finger, assessing range of movement while assessing movements or conjugacy, according to Dr. Samadani.
The eye-tracking technology used in this study was originally developed by Dr. Samadani along with her colleagues at the Cohen Veterans Center to assess eye movement in veterans of the long Middle East wars suspected of suffering from traumatic brain injury (TBI), concussion or other forms of brain injury.
Researchers in the new study evaluated 75 patients (between the ages of 18 and 60) in the emergency department at Bellevue Hospital Center in New York City, who had sustained head trauma and compared them with 64 healthy control subjects. Researchers recorded and then compared the movements of the patients’ pupils for 200 seconds while watching a music video.
Results from the study indicated that 13 patients who suffered head trauma had a CT scan demonstrating evidence of brain injury, as well as 39 patients who suffered head trauma with a normal CT scan, demonstrated a reduction in ability to coordinate their eye movements compared with normal, uninjured control subjects. 23 patients who suffered extremity or body trauma (without head injury) but did not require a CT scan of the brain, revealed similar eye movements and conjugacy as normal uninjured controls.
In the study, the majority of patients who suffered head trauma and had a normal CT scan were still symptomatic 1-2 weeks after their injury, but ultimately recovered about one month after the initial injury. Looking at all patients in the study, the severity of concussive symptoms as measured by the SCAT-3 (Sport Concussion Assessment Tool- 3rd addition) and SAC (Standardized Assessment of Concussion)—both standardized exams for concussion assessment– correlated with the severity of abnormal eye movements or dysconjugacy. This validates the utility of such a tool for assessment for symptom improvement and return to play decisions.
Richard G. Ellenbogen, MD, The Theodore S. Roberts Endowed Chair and professor and chairman of the Department of Neurological Surgery at University of Washington Medicine and co-chair of the Head, Neck and Spine Committee of the National Football League, who was not involved in the study had a favorable impression regarding the research by Dr. Samadani.
“Traumatic brain injury is one of the most common causes of neurologic morbidity in the world today,” Dr. Ellenbogen said. “Sports concussion, on the mild end of the spectrum of TBI, has captured the fascination of both the public and media. Since concussion affects all ages, both genders and occurs in all sports, being able to make the diagnosis quickly and accurately is essential. The challenge physicians have in identifying concussion is that the diagnosis is often based on self-reported symptoms.”
Ellenbogen offered additional thoughts on such novel technology, focusing on potential future applications.
“Dr. Samadani and her colleagues have come up with a novel and objective manner of assessing patients with a suspected TBI,” Ellengogen added. “The beauty to their method is that it is non-invasive, reproducible and easy to perform on the sidelines or in the field. It provides a simple and elegant method of being able to assess the functional deficits that occur with TBI, and thus help the physician make a rapid and accurate diagnosis. By tracking eye movements, they have been able to quantitatively assess the function of the brain. Their new approach will hopefully identify those patients who may be missed by basing the evaluation simply on subjective complaints. This work adds an important dimension to our ability to provide safe, rapid and accurate care to those who suffer TBI in sports or with daily life activities.”
Samadani’s recently published research in December, 2014 in the Journal of Neurosurgery, solely evaluating military veterans at Cohen’s Veterans Center in Manhattan, found that the use of such novel eye-tracking technology could reveal edema, or swelling in the brain as a potential biomarker for assessing brain function and monitoring recovery in people with head injuries.
Her more recent research described heretofore, involving civilians in an emergency department, builds upon the principles of the novel algorithms she recently developed and demonstrates proof of concept of such technology.
Future plans by Samadani include evaluation of the eye tracking technology as a diagnostic marker for evaluating TBI among Iraq and Afghanistan veterans with post-concussive syndrome as well as post-blast brain injury sustained in the military.
Additional applications include evaluation of neurodegenerative diseases, including Alzheimers disease and other forms of dementia. Other neurologic conditions from hydrocephalus (swelling of the ventricle in the brain) to benign intracranial hypertension (formerly known as pseudotumor cerebri) are detectable using such technology.
Samadani’s Novel Approach to Eye Tracking
According to Samadani, while eye tracking technology has been used over the past 30 years for neuropsychiatric evaluation and evaluation of brain injury–using saccades, smooth pursuit, or fixation techniques–the specific approach that her team stumbled upon has made her approach unique.
Spatial calibration–the traditional approach for measuring eye tracking–is unique for each patient and requires a subject to follow commands while looking at certain points. With spatial calibration, the relative positions of pupil and corneal reflections as a person looks at specific points are carefully measured to produce useful data associated with pupillary movement.
However, by using temporal rather than spatial resolution for eye tracking, one is able to detect impaired ability to move one pupil relative to the other. By watching a music video moving inside an aperture on a computer monitor, positions of the pupil can be compared at any given time by subtracting their specific Cartesian coordinates.
The true advantage is that non-spatial or temporal tracking not only doesn’t compensate for impaired mobility, but can be used in children, those who are vegetative, aphasic, or those who speak a foreign language. It could even be used in animals.
Barriers to Adoption and Future Applications
Potential barriers to adoption of eye tracking technology for concussion evaluation and management in the ED or on the playing field may potentially affect the adoption of this tool.
“We are currently working on identifying all possible “confounders” of ocular motility or its assessment that will impact eye tracking results in a general population,” explained Samadani. “We already know that things such as toric contact lenses, heavy mascara, poor visual acuity and strabismus can impact tracking.”
She went on to explain that “we are working on fine-tuning our mathematical algorithms to decrease the impact of artifacts introduced by these processes.” “Emergency department use has relatively few barriers, because one can control ambient light, so locker room use is also feasible for that reason. Sideline use may be slightly trickier because of the variability in ambient light.”
Another issue is whether such eye tracking technology can be used via an app in the home or office setting for uploading to a larger portal, such as a cloud, for purposes of telemedicine and wider access.
“We are planning on developing an app for consumer use,” offered Samadani. “But first we need to get FDA clearance of our current device for medical use, but this is definitely in the pipeline.”
Use of a portable and deployable mode to apply eye tracking technology remotely argues for development of a headset for ease of data acquisition. Samadani explains that this is a future goal of her company, Oculogica.
Sean Grady MD, the Charles Harrison Frazier Professor and Chairman of the Department of Neurosurgery at the Perelman School of Medicine at the University of Pennsylvania, felt that Samadani’s research is compelling. He was not involved in the study.
“The importance of this study is that it establishes a reliable test and a ‘biological’ marker for detecting concussion,” said Grady. “Since concussion can occur without loss of consciousness, this can be particularly important in sideline evaluations in athletics or in military settings where individuals are highly motivated to return to activity and may minimize their symptoms. More work is needed to establish its sensitivity and specificity, but it is very promising.”
“Two patients who suffer a head injury and present with virtually-identical CT-scans might have completely different symptoms,” Samadani emphasizes. “That’s where eye-tracking can help objectively reveal when one patient may be much more affected by a concussion than another.”