Neil Osterweil

July 05, 2016

BOSTON — A simple, quick test performed with a pupillometer appears to be an effective screening tool for acute mild traumatic brain injury, US Army investigators report.

"We have identified functional divergences that could be biomarkers for traumatic brain injury," said José Capó-Aponte, OD, PhD, from the Department of Optometry at the Womack Army Medical Center in Fort Bragg, North Carolina.

"The next step will be to take those selected components and create an algorithm or calculator" that will estimate the likelihood of a traumatic brain injury, he told Medscape Medical News.

Dr Capó-Aponte presented study results here atOptometry's Meeting by the American Optometric Association.

Of the more than 340,000 cases of traumatic brain injury clinically confirmed from 2000 to 2015, mild injury accounted for 82.5%, according to US Department of Defense statistics.

However, traumatic brain injury is often only identified when moderate or severe head injuries have occurred, leaving mild cases undiagnosed, Dr Capó-Aponte and his colleagues explain in their scientific poster.

"Since approximately 30 areas of the brain and seven of the 12 cranial nerves deal with vision, it is not unexpected that the patient with traumatic brain injury may manifest a host of visual problems, such as pupillary deficit, visual processing delays, and impaired oculomotor tracking and related oculomotor-based reading dysfunctions," Dr Capó-Aponte pointed out.

To see whether they could identify reliable biomarkers of mild traumatic brain injury that could be detected with an easily reproducible screening test, he and his colleagues looked for subtle visual changes that could be measured in the office or in the field.

The investigators settled on conjugate binocular eye movements (versions) and disconjugate movements (vergences) as potential biomarkers.

They tested their hypothesis with a 10-minute test that consists of three eye measurements and one visual symptoms questionnaire.

The case–control correlational study involved 2000 active-duty military personnel 19 to 44 years of age. Of these, 87 men and 21 women experienced a medically documented mild traumatic brain injury or concussion in the previous 72 hours.

Inclusion criteria were a loss of consciousness of not more than 30 minutes, post-traumatic amnesia and/or altered mental state lasting no more than 24 hours, a Glasgow Coma Scale score of 13 to 15, and normal structural brain imaging.

The age-matched control group consisted of 79 men and 21 women with no history of traumatic brain injury.

Monocular Infrared Pupillometry

Testing consisted of monocular infrared pupillometry under dim conditions to measure pupillary light reflex to a stimulus. The investigators measured maximum and minimum pupil diameters, percentage of constriction, constriction latency, average and maximum constriction velocity, average dilation velocity, and time to 75% recovery of dilation.

They also tested near-point convergence with a 20/30 Snellen single-letter stimulus, and tested for saccadic eye movement function with the King–Devick Test. Visual symptoms were assessed with the Convergence Insufficiency Symptom Survey (CISS).

Of the eight pupillary light reflex outcome measurements, only average constriction velocity, average dilation velocity, and 75% dilation recovery time were significantly different between patients with mild traumatic brain injury and control subjects (< .0001 for all three comparisons).

Patients with mild traumatic brain injury also had significantly higher near-point convergence scores (receded near-point convergence) than control subjects, longer times to complete the King–Devick Test, and more symptoms on the CISS (< .0001 for all comparisons).

 
We have been searching for the one thing that will allow us to diagnose the presence of a concussion as quickly as possible.
 

"We have been searching for the one thing that will allow us to diagnose the presence of a concussion as quickly as possible after the incident," said poster moderator Dominick Maino, MD, professor of pediatrics and binocular vision at the Illinois College of Optometry and Illinois Eye Institute in Chicago.

"With the test described by Dr Capó-Aponte, we would have a device that could be easily taught to others, is relatively inexpensive, and would give us immediate feedback on the presence of a concussion," he said.

"Then we can get that individual into treatment as soon as possible, knowing this concussion is present, with all of the ways that it adversely affects the oculovisual system for the individual and their quality of life," Dr Maino told Medscape Medical News.

This study was funded by the US Department of Defense. Dr Capó-Aponte reports that the opinions and findings contained in the study are those of the investigators, and not necessarily those of the Department of Defense or the US Army. Dr Maino has disclosed no relevant financial relationships.

Optometry's Meeting by the American Optometric Association (AOA): Poster 3. Presented July 2, 2016.

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