By: Eric Hussey, OD, FCOVD, Optometric Offices, Spokane, Washington.
We need to talk a bit about brains. An interesting research study came out from the University of Washington that looked at dementia and cataract surgery. The idea was if we get cataracts out of the way sooner, does that make any difference in when dementia develops? It was a pretty tangled statistical study, but the results suggest that removing cataracts earlier might help stall dementia. Makes sense. Vision is something like 80% of the sensory input to the brain. Higher quality sensory input should mean the brain has better data to work with, which also means neurology is presented with sharper visual stimuli, which is what the visual system and then the brain responds to. A more neural response should mean broader and better neuron connectivity. That equals better brain function.
I was also reading about magic recently. Two visual neuroscientists, Stephen Macknik and Susanna Martinez-Conde not only wrote a book about magic but became magicians – they’re part of the magician’s union, I think, called the Magic Castle. In their book Sleights of Mind, they talk about how brains construct reality. Brains construct or calculate reality from sensory input in a context allowed by memory and habituation. Thinking will construct reality, but thinking is energy-intense and energy-expensive. If sensory input is reliable over time and accurate in its details, calculation decreases, and thinking and attention can move to other tasks. I added the “reliable over time” part.
You may not consider thinking to accomplish every task is such a big deal. But have you ever heard the old line that goes, “he can’t chew gum and walk at the same time?” Think about that for a moment (speaking of thinking). Imagine if you had to think “chew once” followed by “now take a step” followed by “chew once”… If you had to actively direct each act by actively applying attention and thinking to that act instead of using memory and habituation, you’d never make it out the front door of the Quickie-Mart where you bought the gum.
The point is surprisingly simple. Brains rely on accurate data (visual input) to form visual reality for each person. If that data input is impaired by cataracts or by the intermittent central suppression we deal with in kids with reading problems (and adults with head trauma), then the owner of that brain must use far more brain resources and energy to do things. Is it any wonder that kids with intermittent suppression will prefer PE and recess to reading? Is it any wonder that adults with acquired ICS from whiplash will talk about how tiring driving in new surroundings can be? They can’t rely on more automatic habituation and memory but have to constantly rely on active calculation by the brain with the limited or defective sensory input it has.
The good news is both conditions, cataracts and intermittent central suppression, are treatable: cataracts by surgery and intermittent central suppression by therapy. I recommend cataract surgery earlier than I used to because of the research I discussed above. When someone shows intermittent suppression, I try to make sure that they know the only treatment we have currently is vision therapy. We’ve done the research to know that lenses alone can’t fix it. But therapy is very successful in treating suppression. Details on that are probably fodder for another blog post.