US researchers have shed new light on the processes that damage vision during stroke. Ultimately, this better understanding of the connections between the brain and the eyes could help develop new therapies.
Every year around the world, nearly 5 million people die from a stroke while 15 million suffer a non-fatal attack. And among them, 60% are coping with eye disorders. Because when a crisis takes place in the primary visual cortex, which records the visual information, the lack of blood oxygenation damages the active neurons of this area. And thanks to an American study published on February 27 in the newspaper Proceedings of the Royal Society B, today we know much more about the mechanisms at work in the damage of vision during a stroke.
In this study, researchers from the University of Rochester followed 15 people treated in US hospitals for vision problems following an attack. They subjected them to vision tests and scanned them for brain activity and examination to study their retinal ganglion cells.
They found that their health and survival depended very much on activity in the associated primary visual area. As a result, retinal cells connected to the inactive areas of the brain would atrophy during an attack. However, the team noticed that some retinal cells in the participants' eyes remained healthy and functional, even after the person lost his sight in this part of the eye.
Exploit the plasticity of the brain for a return of sight
Thus, these healthy cells remain connected to fully active cells in the visual cortex. However, neurons fail to correctly interpret the visual information they receive from retinal ganglion cells. This is why the stimuli does not translate more correctly, explains the study.
"While an attack may have damaged the transmission of information from the visual center of the brain to larger areas, these findings prove that when the primary visual center of the brain is intact and active, clinical approaches that exploit the plasticity of the brain can lead to a return of vision, "notes Dr. Bogachan Sahin, Ph.D., assistant professor at Rochester University who participated in the study.
"These results point to a treatment that would involve a vision field test and an eye exam to identify the discordance between visual impairment and degeneration of retinal ganglion cells," says the lead author of this study, the Dr. Colleen Schneider. "This could identify areas of sight with intact connections between the brain and the eyes and this information could be used to develop vision training therapies for damaged areas that are most likely to be repaired. "she continues.
Correctly rewire damaged connections
"By better understanding what connections between the eyes and the brain are still intact after an attack, we can begin to explore more therapies to encourage neuroplasticity with the ultimate goal of giving patients more vision," concludes Dr. Brad Mahon. who conducted the study.
In the long term, researchers hope that their discovery will allow specialists to refine therapeutic approaches or develop better strategies to stimulate brain-damaged connections to "rewire" properly.
In research on vision disorders after stroke, the University of Rochester is an institution. In 2016, his scientists created a new form of brain rehabilitation after stroke, in the form of a computer program of visual stimulation, for people with so-called cortical blindness (an impairment of visual perception due to a lesion in the body). primary visual cortex), to stimulate and regenerate this part of the brain. Thus, each patient is subjected to projections alternating points and light streaks in his "blind zone". According to the study published in 2017 in the journal Neurologyif at the beginning the participants guessed what they were supposed to see, over the course of the sessions (the program lasts at least three months), they managed to see enough to correctly answer 80% of the test, the same score as the people with normal vision. On average, at the end of the experiment, patients had recovered 108 degrees of vision.