Why is squinting so difficult?

Well. Why is so difficult to squint on purpose and why does it hurt? I can move my eyes around with no problem, but only both eyes simultanious. Moving just one eye is impossible for me and too much squinting will hurt.
Is it just because I’m not used to do this or is there a physical connection between my eyeballs?


Welcome, Nils, to the Boards. Darn good question you ask, and I’ll give it a shot, although I’m no opta–opto–aw, heck, eye doctor.

Squinting doesn’t hurt me at all–I do it all the time when I’m outdoors and the sun’s out. I’m dead sure I’m doing it on purpose, because if I don’t, it hurts my eyes. Same thing happens when I get up in the mornings before dawn; I turn on the light and I have to squint to see anything. It hurts like crazy to have a lot of light hit the retinae and squinting filters out enough that I can get dressed and drag myself to the shower.

And the reason both eyes move together lies in the brain, specifically, our visual cortex. Unlike chameleons, humans can’t process two visual images at the same time. Our brain forces the two eyes to work together.

Now, let’s wait till someone smarter comes along and explains this in better detail.

What do you mean by “squint on purpose” and how is this related to the ability to move both eyes simultaneously? I suppose you know that when you squint, you’re attempting to reshape your eyeball with the muscles surrounding your eyes to sharpen focus.

Well, I guess my dictionary played a trick on me here. I looked up “schielen” and it gave me the English translation to be “to squint”. I also tried several online dictionaries with the same result. But one of them also suggested “strabismus” which seems and “to be cross-eyed” (which doesn’t sound very PC to me). I think this comes closer to what I wanted to ask:

Why is it so difficult to move each eyeball seperately?

If I try to, it will hurt a little, why?
I’ll try a little ascii art to illustrate better what movement I mean


my eyes are very flexible. i can cross both eyes or just one at a time. i took a while to learn though-i wasnt born this way. so maybe its just due to practice. like any other muscle, straining hurts, but maybe ive excersised my eyes more making them more flexible

I always thought squinting improved focus the same way as looking through a pinhole… the smaller aperture means the light that you see comes from a smaller range of angles, or something like that.

Nils: squinting is what you do in bright sunlight, or if you’re trying to read without your glasses. Crossing your eyes means making both eyes point towards the bridge of your nose. (I don’t think there’s a word for making both eyes point outwards, i.e. towards your temples, because not many people can do that.)

I can cross my eyes, but I can’t otherwise move my eyes independently. Crossing them is the only way I can get them to point in different directions at the same time.

I can cross my eyes quite easily, without even having to focus on anything to do so. However, I can’t move them independently any other way.

You can give the ‘optical illusion’ (ha) of being able to move your eyes independantly, Indefatigable , by doing this …

Cross your eyes by looking at your nose, look full left, cross your eyes again, look full right. Repeat as necessary.

You will have to ask someone else what it looks like though. Good party-trick huh?