Four million people suffer a traumatic brain injury (TBI) annually in the United States. About 75% of those are considered mild (mTBI).
TBIs were the hallmark injury of the Iraq/Afghanistan wars with 250,000 new cases reported annually between 2000 and 2010. In both military and civilian populations, when TBI patients are asked to fill out a symptom inventory, about 80% of them will self-report difficulty reading or other vision problems and/or sensitivity to light despite having normal visual acuity and fundus examinations. About 50% of those patients continue to have symptoms five years after injury.
These chronic symptoms result in disabilities and loss of productivity which lead to a cost of up to $76.5 billion annually in the U.S. from direct expenses and lost income.
“Multiple studies have detected ocular motor deficits in TBI patients, which could underlie the difficulty reading. Unfortunately, tests of ocular motor function have not been adopted into the clinic to diagnose TBI patients,” said Tonia Rex, PhD, professor of Ophthalmology and Visual Sciences. “Instead, if a TBI patient is referred to an eye specialist, their visual acuity is tested and they undergo a fundus exam, both of which are typically normal.”
Multiple assessments of the visual system, combining a test battery and use of a machine learning algorithm, should be included in an mTBI diagnostic battery, she said.
Rex, who holds the Marlene and Spencer Hays Directorship in Translational Vision Research, led a Department of Defense (DOD)-funded study using this approach. Findings from that study were recently published in JAMA Ophthalmology in the article, “Primary Visual Pathway Changes in Individuals with Chronic Mild Traumatic Brain Injury.”
The impetus for applying for funding from the DOD was coming up with a different approach to diagnose TBI patients who were self-reporting vision problems, she said.
In the study, which included 28 participants with mTBI and 28 control patients, deficits in ocular motor function and/or changes in the structure and function of the primary visual pathway were identified in 78% of participants with mTBI. Machine learning identified deficits in the posterior visual pathway in 72% of participants with mTBI, and in both cases, findings were present regardless of self-reported visual dysfunction.
The study was performed primarily on civilians but is relevant to the military and veteran population, Rex said.
“Through my research on visual system neurotrauma, I had the opportunity to meet service members and veterans who were struggling with TBI-associated vision problems. They expressed their frustrations to me,” she said. “The common theme was that they would go to an optometrist or ophthalmologist because of their symptoms and were told that they were fine, and nothing could be done. Worse than that, sometimes they were referred to mental health. Further conversations with practitioners showed me that they were equally frustrated they couldn’t help these individuals. I decided that we, as a medical community, needed a different approach to diagnose TBI patients who were self-reporting visual problems,” she said.
“What surprised me most was that using these approaches, the study team was able to identify TBI patients as different from controls even if they didn’t self-report vision problems,” Rex said. “Thus, identifying changes in the visual pathway may be sufficient to diagnose mild TBI in general.”
If ocular motor function deficits are detected, patients can be referred to occupational therapy for exercises, she said.
The study gets clinicians closer to diagnostic tests for mTBI patients and TBI patients of all severities who are struggling with vision issues, but “we’re not at the level of clinical translation yet,” Rex said.
She and her team recently received new funding from the DOD that will allow them to further refine their machine learning algorithm with a larger dataset.
“Our hope is at the end of this study we will have a diagnostic test for these patients. In the meantime, standardized quantitative ocular motor testing should be performed by trained orthoptists to at least capture and help that cohort through referral to occupational therapists. Truly cross-disciplinary, collaborative large team research can solve challenging medical problems.”
