Thursday, August 28, 2014

The eye doctor and seeing

H. had another eye appointment today. The difference between now and two years ago is slightly astonishing. Two years ago, H. had no idea what we were doing or why and, despite having an interpreter present, we had no real way of explaining it all to her. It was baffling and frightening; just one more baffling and frightening experience that she endured in those first six months. Today, she understood why we were there, what eye drops were and why she needed to have them, the ability to express how much she didn't like them, and the self-control to allow them to be put in her eyes. It was also the very first time that the doctor was able to correct her eyesight in her good eye to 20/20. We have a new prescription and are just waiting for the new lenses for her glasses to be made.

I have also been thinking about the improvement in her eye sight since she has been home. Why should it be getting better? It's not like we are patching to strengthen the good eye. Aside from wearing glasses, there has been nothing that we have done to help her vision improve and yet, we see small changes to the positive each time. It seems odd. Yet, I don't think it really is. Living with H. over the last two years has been like slowly watching a metamorphosis. Actually, is has been a metamorphosis and not just like one. H. is so much more aware of herself and her place in the world now. She understands things that she never understood before. She is learning that she can have opinions and can like things and dislike things. The world is slowly opening up for her even as she opens as a person.

I've always had a sneaking suspicion that so much of what happens inside our heads is interrelated. You can't just separate out sight from memory from physical ability; it all seems somehow interrelated in that mass of brain cells we keep inside our skulls. Since this is my made-up hypothesis, it has no basis in any research what-so-ever, but still it seems to make sense. Imagine my pleasure, then, when I come across something that seems to support my own made-up pet theories. I came across something rather interesting in the book I'm currently reading, Proust was a  Neuroscientist by Jonah Leher. (It's thesis is that certain artists predicted truths about the brain that science is only now discovering. Fascinating.) Anyway, this little bit has to do with how we see. Instead of paraphrasing, I'll share the few paragraphs with with.

"So far, the story of sight has been about what we actually sense: the light and lines detected by the retina and early stages of the visual cortex. These are our feed-forward projections. They represent the external world of reflected photons. And while seeing begins with these impressions, it quickly moves beyond their vague suggestions. After all, the practical human brain is not interested in a camera-like truth; it just wants the scene to make sense. From the earliest levels of visual processing in the brain up to the final polished image, coherence and contrast are stressed, often at the expense of accuracy.

Neuroscientists now know that what we end up seeing is highly influenced by something called top-down processing, a term that describes the way cortical brain layers project down and influence (corrupt, some might say) our actual sensations. After the inputs of the eye enter the brain, they are immediately sent along two separate pathways, one of which is fast and one of which is slow. The fast pathway quickly transmits a coarse and blurry picture to our prefrontal cortex, a brain region involved in conscious thought. Meanwhile, the slow pathway takes a meandering route through the visual cortex, which begins meticulously analyzing and refining the lines of light. The slow image arrives in  the prefrontal cortex about fifty milliseconds after the fast image.

Why does the mind see everything twice? Because our visual cortex needs help. After the prefrontal cortex receives its imprecise picture, the 'top' of the brain quickly decides what the 'bottom' has seen and begins doctoring the sensory data. Form is imposed onto the formless rubble of the V1 [the first stage of the visual cortex in the brain]; the outside world is forced to conform to our expectations. If these interpretations are removed, our reality becomes unrecognizable. The light just isn't enough." (pp. 107-8)

So, what this is saying is that we see things and then our brains translate what the images are into something it recognizes. It is far more than our eyes acting like a camera lens. Interesting, huh? Wouldn't it make sense that a brain that is more aware of the surrounding world would see better? I think so.

This isn't to discount the fact that the images we are taking in with eyes need to be in focus. Considering my glasses prescription, it would be crazy for me to state otherwise. But there seems to be so much more to seeing than what our eyes take in.

1 comment:

Lucy said...

I think the reason people (mostly kids, often adults) stare at someone or something that is very different is because the brain is trying to make sense of what is seen.

For the sake of "politeness" we teach our brains to shut the heck up, maybe take a quick picture for processing later. But that is one reason I am thankful you and others bravely share pictures of your children who are different. I can show my kids the pictures, and explain and let their brains process as slowly as needed without anyone being uncomfortable. Then when they see real life, their innate processing time is much faster.

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