Yesterday I had my follow up eye exam. Late last year I had a “blind spot” appear in my vision, that turned out to be a cotton-ball spot inducing a floater. Yesterday was the follow up, and long story short, the eyes are fine (the spot is gone, and no new ones).
To check my eyes, both times my eyes were dilated. The drops they use paralyze the iris muscles, and as it turns out, also paralyze the ciliary muscles. The first time I didn’t know this, and only found out when I was unable to focus close at all. What surprised me most, was my active focus range was totally unaffected, indicating to me that my version of Active focus does not involve the front of the eye.
This time, I came prepared. I wanted to see what accommodation range I had while the front of my eye was paralyzed. What I found surprised me. Once again, active focus was unaffected. Sure enough, nearer accommodation was (mostly) inhibited. However, when I tried to close focus (vs let it happen "naturally), I found I could indeed get a little accommodation (about 1 diopter, according to the Meow-Sure app). More importantly, however, the slight sensation on my eye when it finally kicked in was similar to active focus, and different than normal close accommodation.
This led me to a theory I have now that finally answers several nagging questions, mostly around why some people get myopic and others don’t (for similar levels of close-up). What I realized, is that that 1D of “extra” accommodation is likely my oblique eye muscles acting as an antagonistic pair. Since they’re balanced, my eye doesn’t rotate, but acts like a ring around the eye, squashing the “equator” and thus lengthening the eye (causing the “accommodation”. Think about taking a water balloon, wrapping your fingers around the middle like a ring, then squeezing, what happens to the balloon’s ends? Active focus, from my guess, is the rectus muscles all pulling on the eye, squashing it along its axis, yielding a little more distance focus, kind of like holding a balloon on your belly, and pulling on the edges of it towards your belly (the balloon flattens a bit).
It is my personal belief these two forms of accommodation drive eyeball shape size over time. Extended oblique use squashes the eyeball leading to eyeball lengthening (we call this progressive myopia). Extended rectus use squashes the eyeball in the other way leading to eyeball shortening (we call this progressive hyperopia, and I believe use it to undo myopia).
So, given this wacky idea, how does it explain why some get myopia and others don’t? Well, extended closeup with just the ciliary muscle leads to ciliary muscle fatigue, which means you no longer can focus that close (until your ciliary muscles get some rest). Those of us who “figure out” how to use the obliques to get extra accommodation use that and keep doing close-up for longer. Those who don’t will likely go do something else. By figuring out how to get an extra “kick” from the obliques, many of us extend near focus time dramatically. Why can us myopics do close-up for hours, while our “perfect vision” friends cannot (they get tired of it after a while)? However, the downside is over time the eyeball squashing leads to eyeball changes and thus myopia. Our 20/20 friends never figured this “trick” out and thus only use ciliary muscles to accommodate, and never got on the myopia conveyer belt.
I have no idea if this is right or not. But finally I have a working theory that explains everything (why myopia occurs, why we can reverse it, why some never get near-sighted, and how that all works). And it’s backed up by my experience of having my eye front (iris and ciliary) paralyzed, yet still able to accommodate both plus and minus a bit. It even explains why those who get cataract surgery sometimes can still accommodate close up a bit despite rigid pupils that are no longer affected by the ciliary muscle (they might do it by obliques squishing the eyeball causing the retina to move back from the lens).
And that’s cool, finally a mental model on the eye’s behavior that addresses pretty much all the mysteries I’ve had about it
Now, someone please shoot down my ideas for me