Visual Processing – Part One – The Mechanism Within
A question often posed in the Vision Therapy room involves an understanding of how a particular activity applies, or perhaps more directly stated, “what does this have to do with my eyes?”. Although genuine, the question identifies a chasm in understanding between eyeballs and brain – or to be a bit more cliche – between sight and vision. Working on eyes involves tools such as lenses, prisms, eye patches, swinging balls, and even letter charts. Throw in a metronome and a walking rail and you’re in business. From the outside looking in, it seems to make sense. So now what’s with the blocks? Why do we care if you can copy my pattern? Shouldn’t parents teach their kids about left and right? How does logical thinking apply to my child’s eyes not moving across a page efficiently? What does thinking have to do with any of this?
(For those who think the answer is “May”, you’re wrong. Find out why in Part 2)
The answer is simple, and yet difficult.
First the simple…
Our eyes take a picture, the picture gets transmitted to our brain our brain decides what to do with the picture and finally, a reaction is created. This reaction might be as simple as stopping a marble as it rolls on the ground, or it could be as complex as using visualization to flip and rotate. No matter the demand, this process generally involves decisions which may include filtering which areas information is of value, which parts of the picture might be discarded, and which pieces to store in our memory banks for another time. All of this occurs sometimes in hundredths of a second. Every thing we do during the day from brushing our teeth, to locking our car doors, to shopping for groceries is a replication of this process. It’s a pretty fascinating mechanism when you stop and think about it. Given all of this, if our eyes are transmitting a picture which is in some way flawed, either because it’s blurry or even inconsistent, our ability to create an appropriate reaction will be altered due to receiving incomplete or inaccurate information. It reminds me of being a child and trying on my grandmother’s glasses. The world looked a mess! I could still function, but clearly not at the same level as when the world was clear, single and my brain was receiving an easy to decipher picture.
And the more complex…
Most of us have schemes for problem solving, be it for unlocking a door, finding our way in a strange neighborhood, or even solving mathematical equations. These schemes are influenced by, among other things, our logical deductions and past experiences. When things look the same as they did the last time we were here, our logical deduction concludes the solution must also be the same, or at least we may think that way. Although we tend to fall back on this thinking quite often, unfortunately, it doesn’t always work. As an example, the front door to my house is red and the keys in my pocket open that door. Is it safe to assume therefore my keys will open all red doors? Some would say yes, even though past experience demonstrates it may not be accurate. And so we reach a conundrum, which in most cases is resolved through our sensory inputs – visual, auditory, touch, smell and taste.
This may be an opportune moment to mention vision is the dominant sense of the five.
Although the doors may appear the same in many ways, the keys look and act differently. Faced with this issue, we now have to gather more information. It’s highly doubtful the taste, and smell of the door will come into play, although if they do I’d be interested to understand more. Auditory input may include the sound of a locked door when it is knocked upon, although we would quickly realize a locked door sounds the same as an unlocked door, plus in this situation knocking produces no results. How the door feels to the touch won’t help us open it, so we’re left with vision. What information is gathered visually which helps us get the door open?
As an experiment, put your keys in your pocket, go out your front door, and be sure it locks behind you. Once locked outside, work on getting back in the house with your eyes closed. You have both logical reasoning (assuming you know how to unlock a door) and past experience (assuming you’ve lived in your home more than a few days) on your side so it shouldn’t be too tough. You’ve been there before, you know how to open a door, except this time we’re removing the dominant input for resolving problems. How easy will it be to find the correct key? Which other senses will you rely on to determine where the keyhole is and when the door is open? How much longer does this process take when we take away the benefit of vision?
My point here is the process of visual collection and processing cannot be overlooked when treating a visual system. Vision truly is a two-way street. We gather information from outside to inside as much as we look for things to interact with from the inside out. And so, when a parent asks me how a particular activity (which ostensibly appears unrelated) helps a patient’s eyes, my common response is “it doesn’t”.
“We’re after way more than just 20/20…”