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Vision problems could be identified using comprehensive optical assessments and machine-learning approaches among people with chronic mild traumatic brain injury (TBI), a prospective, observational, case-control study suggested.

In 28 participants with mild TBI that occurred a median of 6 years earlier, workup showed reduced prism convergence test breakpoint (-8.38, 95% CI -14.14 to -2.62, P=0.008) and recovery point (-8.44, 95% CI -13.82 to -3.06, P=0.004), reported Tonia S. Rex, PhD, of Vanderbilt Eye Institute at Vanderbilt University Medical Center in Nashville, Tennessee, and colleagues.

These participants also had decreased contrast sensitivity (-0.07, 95% CI -0.13 to -0.01, P=0.04) and increased visual evoked potential binocular summation index (0.32, 95% CI 0.02-0.63, P=0.02), they wrote in .

"As TBI is inherently complex, diagnostics need to be multimodal. The combination of a test battery and use of machine-learning algorithms will allow us to reach the necessary specificity and sensitivity to accurately diagnose these patients," Rex told MedPage Today. "Our hope is that we will have a diagnostic test for these patients" after further research, she added.

An estimated 4 million people in the U.S. suffer TBI each year, the authors said, and about 75% of cases are mild.

According to Rex, about 80% of patients with TBI report vision problems, such as difficulty reading and sensitivity to light. "Multiple studies have detected oculomotor deficits in up to 75% of TBI patients, which could underlie the difficulty reading," she said. "Unfortunately, tests of oculomotor function have not been adopted into the clinic to diagnose TBI patients. Instead, if a TBI patient is referred to an ophthalmologist, their visual acuity is tested, and they undergo a fundus exam, both of which are typically normal."

Rex's own encounters with patients suffering from TBI have revealed how their vision problems can be missed. "The common theme was that they would go to an optometrist or ophthalmologist because of their symptoms, but were told that they were fine and that there was nothing that could be done," she said. "Worse than that, sometimes they were referred to mental health."

It's clear, Rex noted, that "we need a different approach to diagnose TBI patients who are self-reporting vision problems."

For now, she added, there are no recommendations about a specific battery of tests for patients with TBI, although she and her team hope to develop one. "In the meantime, standardized, quantitative oculomotor testing should be performed by trained orthoptists to at least capture and help that cohort through referral to occupational therapists," she said.

However, the situation may be more dire for patients with damage to the retina, optic nerve, and brain, which the study authors detected. "Unfortunately, central nervous system neurons do not regenerate. My laboratory and others are investigating neuroprotective and neuroregenerative approaches," Rex said.

In an , Madeleine K. Nowak, PhD, of the Translational Research Center for Traumatic Brain Injury and Stress Disorders at the VA Boston Healthcare System, and colleagues noted that "this study marks significant progress in identifying visual impairments in patients with chronic mild TBI."

While "the optimal battery of tests to assess the visual system following mild TBI has yet to be decided," they wrote, the findings suggest that "extending the typical eye examination to include OCT [optical coherence tomography], MRI, and machine learning may improve the identification of neurophysiological damage and provide validation for patients reporting visual problems or light sensitivity, even when routine clinical tests return normal results."

Nowak and colleagues also pointed to an "important" study limitation: It excluded participants with a history of neurological or psychiatric disease. "Disorders like posttraumatic stress disorder, attention-deficit/hyperactivity disorder, and anxiety are known to contribute to visual disturbances, light sensitivity, and hypersensitivity reports," they noted.

Future research, they added, should include these patients to get a better handle on how visual disturbances due to mild TBI may interact with other conditions.

For this study conducted from May 2018 to November 2021, Rex and colleagues included 28 patients with chronic mild TBI from a level 1 trauma research hospital (mean age 35, 53.6% men, 64.3% white) and 28 controls without TBI (mean age 35.8, 67.9% women, 32.1% white).

Exclusion criteria included a history of ocular, neurological, or psychiatric disease; moderate-severe TBI; recent TBI; metal implants; age younger than 18 years; and pregnancy.

Assessments included the Neurobehavioral Symptom Inventory and measurements of oculomotor function, OCT, contrast sensitivity, visual evoked potentials, visual field testing, and MRI.

The authors reported that a subset of participants were also shown to have reduced peripapillary retinal nerve fiber layer thickness, increased optic nerve/sheath size, and brain cortical volumes.

They noted that their study doesn't prove any connection between mild TBI and visual dysfunction, and it did not control for time since injury, comorbidities, or variations in number of TBIs.

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