What is the link between traumatic brain injury (TBI) and vision? That’s the question Amanda Henderson is trying to answer.
As medical director of the neuro-ophthalmology division of Wilmer Eye Institute, Johns Hopkins Medicine, she often sees patients who have been told by physicians that they are structurally normal, yet they are experiencing what are often life-changing symptoms — such as headaches or severe sensitivity to light — that prevent them from doing their jobs, taking care of their families or conducting normal daily activities. “We have no good way to treat these patients now, yet they have a condition that’s preventing them from living their lives,” she says.
Henderson, in collaboration with Mary Johnson, a Wilmer alumna and associate professor at the University of Maryland who specializes in clinical applications of electrophysiology and psychophysics, and Arthur Shapiro, a psychology professor at American University who specializes in visual perception and neuroscience, is working under the hypothesis that visual symptoms of traumatic brain injury are caused by a defect in the normal inhibitory pathways in the retina or the brain. “In other words, a problem with the normal filtering of visual information leads to an information overload,” Henderson says.
The hypothesis was developed after initial testing indicated there may be changes in these inhibitory pathways following TBI. The theory, Henderson says, could account for symptoms that patients are describing for which there is otherwise no explanation. “It’s not like I see a patient with TBI and I say, ‘your optic nerve is abnormal,’ or ‘you have an abnormal finding on your MRI,’” Henderson says. “These are patients who are structurally, from everything we can detect even with all of our advanced imaging, completely normal.”
In order to test the hypothesis, the team is seeing how patients from Wilmer and University of Maryland react to computer-based visual illusions that have been developed by Shapiro specifically for this project to evaluate specific parts of the visual pathways. Patients are shown the visual illusions on a computer monitor and are asked to sort images based on their contrast and perceived motion. The team will compare the findings from these patients with those of people without traumatic brain injury.
The evaluations, which started in recent months, will continue over the next few years. “Ultimately, I hope that what we find out can help us develop targets for treatments for these patients,” Henderson says.