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Answer transcribed from Brightway's Interview with Dr. Bryce Appelbaum:
That's a really common question. If we're thinking of a concussion as bruising of the brain, the brain is not going to be functioning the way that it was prior to that injury. There's damage to the pathways of the brain from head injuries that are pathways that are highly organized neuronal networks. I think one of the biggest disruptions that we see in our field is the disruption between the focal and ambient visual processing pathways. The focal pathway responds to central focal information and the ambient pathway responds to peripheral, external information. In a normal healthy brain, because these systems are wired together, I can look straight ahead and know what's going on around me because I'm taking in all of this space simultaneously. Those pathways can be simplified into the “what” and “where” pathways. The “what” is how we focus our eyes with our internal muscles responsible for clarity, or the accommodative system. The “where” pathway is the eye coordination pathway which lets us know where to aim our eyes along the z-axis to align our eyes where our target is.
In response to the question about reading, working, and what happens on a computer: a computer is a fixed distance that, for somebody in the absence of a head injury, provides visual stress. If you don't have the tools in place to meet the demands of visual stress, you're going to notice eye strain, fatigue, double vision, blurry vision, and things like that. I think the perfect time to talk about this is now, where so many kids are now learning from home on the screen and so many adults are working on screens and don't have the visual skills and abilities to support that type of demand. Ocular focus, which would allow for that kind of blurry vision, is intimately related to cognitive focus and visual tension. If you can't keep your eyes focused on one plane or one position, your mind is going to follow and have to disengage.
Concentration requires really careful synergy between the focusing eye teaming and tracking systems in order for the brain to stay engaged in attending to the information that your eyes are sending to it. That said, vision therapy helps to group all of those systems together and make sure that they're working in tandem. The goal is to eliminate bad habits, mismatches, and equalize the skills between each eye so that when both eyes are open, neither one is taking over. That kind of binocular rivalry or competition over sensory input and which eye to use, which is really common after a head injury, is no longer an option.
As simple as that sounds, you can't teach a brain or train a brain to use one eye in the presence of the other or to ignore input from one eye to get rid of some of this competition or confusion. So when our brains take the path of least resistance, learn how to operate the way in which they're wired, and bad habits are eliminated as options, then essentially you're restoring visual functioning just like any therapy, whether it's psychological, physical, or occupational. With vision therapy, if there's the appropriate motivation, compliance, and evaluation to actually assess an accurate prognosis, it works and makes it so that those adaptations from the past are essentially no longer options.