How vision can help diagnose concussions

Stock image above is © Aspen Photo / Shutterstock.com. The University of Maine and corresponding sports team and players depicted are not directly associated with this article or the content therein.
 

New York City-Sports-related concussions can now be diagnosed on the sidelines using a two-minute vision-based test, according to a recent study published in The Journal or Neuro-Ophthalmology.

King-Devick test

In recent years, athletic trainers working with athletes in sports such as boxing and martial arts have supplemented the Standardized Assessment of Concussion (SAC)-a test of cognition-with the King-Devick test, in which the injured party reads lines of slightly jumbled numbers on three cards as quickly as possible. The test measures rapid eye movement, visual tracking, and related cognitive responses. If an injured athlete reads the numbers slower after a head impact than in baseline testing, he is considered to be concussed.

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“For decades, optometrists have used the King-Devick test to aid in the diagnosis of ocular motor dysfunction and a need for vision therapy,” says Marc Taub, OD, MS, FAAO, FCOVD, chief of vision therapy and rehabilitation and supervisor of the residency program in pediatrics and vision therapy at Southern College of Optometry. “It is reliable and easy to perform in patients of any age or cognitive ability.

“I personally use this test in my standard binocular vision assessment,” he says. “There are three test plate plates, which increase in difficulty in a step-wise manner. This helps me determine exactly how much difficulty in the patient is having with his eye movements.”

Next: The study

The study

Researchers at New York University’s Langone Concussion Center investigated how adding the test could help identify concussed athletes on the sidelines at both youth and collegiate levels.  

To do this, researchers recruited 243 young athletes between the ages of 5 and 18 and 89 college athletes, all of whom played hockey or lacrosse.

The athletes underwent preseason baseline assessments using:

• King-Devick test

• SAC

• Timed tandem gait test of balance

Related: Vision-based test vital for concussion screening

The SAC and timed tandem gait are components of the currently used Sport Concussion Assessment Tool, 3rd Edition. In the event of a concussion during the athletic season, injured athletes were retested on the sideline or rink-side. Nonconcussed athletes were also assessed as control participants under the same testing conditions.

Next: The results

The results

According to the study, among the 12 athletes who sustained concussions during their athletic season, King-Devick scores worsened from baseline by an average of 5.2 seconds. The vision-based King-Devick test showed the greatest capacity to distinguish concussed vs. control athletes based on changes from preseason baseline to post-injury.

“Adding a vision-based performance measure to cognitive and balance testing enhances the detection capabilities of current sideline concussion assessment,” the study’s authors write. “This observation in patients with mild traumatic brain injury reflects the common involvement and widespread distribution of brain pathways dedicated to vision."

Related: Treating patients with brain injuries

A recent New York Times article on concussion testing stated that the King-Devick test requires no medical training to administer, but Dr. Taub cautions against that statement.

“While the test is standardized in terms of the time to complete each test plate, proper observation by the test taker is crucial in picking up other signs of the concussion,” he says. “Working with an optometrist who routinely uses this test and can perform vision therapy to rehabilitate the concussed athlete is a key aspect of the treatment process.” 

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