Health

The Brain chooses the path of least resistance

Published 8.31.2017
This is an entirely personal post, and one that doesn't relate to most of the topics I write about here. However, it is what is flowing from my fingertips, so it is what it is.

I had an eye appointment, at which I learned that I have mono-vision. Mono-vision means that I only use one eye to see. My vision is poor, and has been my entire life. I've worn eyeglasses continuously since about age 6, with the exception of a couple years in high school when I refused to wear them for reasons that are beside the point in this piece.

The vision in my two eyes is also very different, with a severe astigmatism in one eye that is so severe it can't be completely corrected. The brain, the doctor told me goes with the information source that requires it to do the least work. Functionally, this means that my brain uses the information from my left eye (the eye that can be corrected to 20/20) and discounts the information from my right.
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I knew that my brain used my two eyes differently, I realized this in eighth grade after doing an experiment on myself. Thinking I'd actually discovered something new, I repeated the (simple and harmless) experiment on classmates. Basically, most people's brains use information from both eyes when looking near or far, but my brain, because of the huge difference between my two eyes, uses whichever provides the clearest image. Without correction, the choice my right eye. With correction, the choice is my left.

This suggested (to the doctor) that perhaps I could wear a contact on the left eye (the one with the least astigmatism that can be corrected completely for distance sight (driving in particular) and then go uncorrected on the right and use that for reading and computer work.

The idea intrigues me, if only because I think that my brain should make use of the input for both eyes. Interestingly, the prescription for my left eye improved by an entire diopter, so the contact and new glasses I get will actually be weaker on the left. The right eye did not change, it has not changed in years. If I start using the right eye more might it improve as well? Time will tell— assuming I can tolerate having to switch between the eye for near and far vision. Because my brain is already used to seeing such disparate signals and choosing between them, the doctor thought I wouldn't have a problem.

The contact fitting isn't until next week, so me being me, I've been running experiments, trying to gauge whether or not a I see well enough with my right eye to leave it uncorrected. Simply taking my glasses off requires my brain to use my right eye more because I can't see anything clearly with the left unless it's six inches from the eyeball. Although I don't see well enough to drive, I see well enough to function, and I can even ready menus and signs. However, the images presented to my brain are not clear, and it has to work a lot harder. I don't see that as a sustainable model.

Thinking that it might be that the blurry signal from the left eye might be complicating the brain's task, I also tried covering my left eye completely. Doing so did help a bit, so it's possible that when my left eye is corrected for distance, its signal will affect the image less. It's also possible though that given that the eye will be corrected the brain will revert to trying to see everything with it.

I've realized that because I stand at my laptop while using it (as I am doing as I type these words) I am using my distance sight, which favors the left, at least when I have my glasses on. If I take my glasses off and cover my left eye, I can still read the text, but it's blurry. The same is true if I hold a book or paper. This suggests that my uncorrected vision in my right eye is not going to be good enough for reading and using the computer.

So what happens if I put my glasses on with the left lens covered so that the left eye can't provide any input? Pretty much the same thing. However it I use the "reading" portion of my progressive lenses, then the text is clear, either on the screen or in a book. I'm not sure the doctor considered the fact that in addition to my distance prescription, I also have a prescription for reading glasses.

My experimental evidence is that I still need the reading glasses (I have progressives). I'm not sure how that will work with contacts. Will I need a pair of reading glasses, maybe with a pane of glass on the left? I can go to the drug store and get a pair of reading glasses at the prescription level I need, but if both eyes have the reading correction, but only the left is corrected for distance, wouldn't my brain still use the left?

Or maybe I should get a pair of glasses with a corrective lens on the left and the reading glass prescription on the right? Normally getting a new pair of glasses isn't so complicated.

The other complication is the size of the frames. Apparently the style is now to wear larger frames. When I bought my current frames (which are larger) the style was to wear smaller frames. The optician warned my that I might have trouble finding the reading glass area on such large lenses, and she was correct. Therefore, I am looking for smaller frames this time. Naturally, they are no longer in style.
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