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Stroke & Vision

Posted by Ilena Di Toro | Posted on May 9, 2017

Most people know that a stroke can affect movement, speech and cognition. What many don’t realize is that it can also affect vision. Post stroke vision conditions include:

Vision Loss—this includes hemianopia, which is blindness in one half of the visual field; quadrantanopias, blindness in a quarter portion of the visual field; scotoma, a island-like area of blindness; bitemporal hemianopia, blindness on the outside half of the visual field.

Vision Perception—this includes double vision; visual midline shift, where the center point of a person’s visual field seems to have shifted either left or right; visual neglect, ignoring a certain part such as the left or right side of the visual field; problems with depth and distance perception.

Oculomotor Dysfunction—also known as jerky eyes, this is when the eyes can’t move smoothly from one point to another.

For a long time, doctors and scientists thought that a person who had a vision problems caused by a stroke would have to deal with compromised vision. Research done at the University of Rochester Eye Institute, however, found that having partially blind stroke patients do visual exercises on a computer every day for several months lead to improved vision.

The study was lead by Krystel Huxlin, Ph.D., a neuroscientist and associate professor at the university. She and her team studied seven patients, ranging in age from their 30’s to their 80’s, who had a stroke that damaged the primary visual cortex portion of the brain. This part of the brain sends visual information to other parts of the brain, which process the information and allow us to see.

When stroke damages the visual cortex, people have a hard time reading, driving or even navigating from Point A to Point B. Yet, despite the stroke, the eyes are taking in correct information. The thing is, the information isn’t properly processed to create vision.

To overcome this problem, researchers focused on training the other areas of the brain not damaged by a stroke, so that visual information is brought to consciousness and the person is aware of what they are seeing. The main research focus was motion perception since it is critical for most tasks. Researchers wanted to see if the middle temporal region, which was healthy and functioning in the subjects, could be trained to do the tasks that the visual cortex does.

The experiment involved the subjects gazing at a small black square in the middle of a computer screen. Every few seconds, 100 dots would appear within a circle somewhere in the subject’s visual field. So, the person had to choose whether the dots appeared on the right or left. A chime would sound when the subject chose correctly. While the person can’t consciously see the dots, they are aware that something is going on. As the subject’s success rate improves, the researchers move the dots further and further into the blind spot, as a way to challenge the brain and make it see a new area.

The results were very promising. Five participants who took part in the experiment had vastly improved vision. They were able to see in ways that they weren’t able to before. Other participants were able to drive again, take up exercise, or resume shopping.

This study shows how elastic the brain is and the importance of visual rehab for persons who had a stroke. Just a person who has a stroke can relearn the tasks of daily living with physical and occupational rehab, a person can relearn how to see with visual rehab.

Sources:

http://www.stroke.org/we-can-help/survivors/stroke-recovery/post-stroke-conditions/physical/vision

http://www.strokeassociation.org/STROKEORG/LifeAfterStroke/RegainingIndependence/PhysicalChallenges/Vision-Disturbances-After-Stroke_UCM_467437_Article.jsp

https://www.urmc.rochester.edu/news/story/2436/rigorous-visual-training-teaches-the-brain-to-see-again-after-stroke.aspx

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