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Uploaded:2019-12-31
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If you've ever tried to make out something that was really far away, odds are you squinted while doing it. It's basically involuntary! But does narrowing your field of vision really help you see things better?

Hosted by: Hank Green

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Sources:
http://www.ccmr.cornell.edu/faqs/why-does-squinting-help-people-with-vision-problems-see-better/
https://journals.lww.com/optvissci/Abstract/2003/11000/What_are_the_Visual_Benefits_of_Eyelid_Squinting_.9.aspx
https://www.nature.com/articles/ncomms15683
https://meded.ucsd.edu/clinicalmed/eyes.htm
https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/refractive-errors
http://scienceline.ucsb.edu/getkey.php?key=2577
https://jkms.org/DOIx.php?id=10.3346/jkms.2017.32.5.850#
https://iovs.arvojournals.org/article.aspx?articleid=2166618
https://www.casewatch.net/ftc/news/1993/natural-vision.shtml
https://journals.iium.edu.my/ijahs/index.php/IJAHS/article/view/105
♪♪♪.

So...squinting. It's a thing that we do.

Something looks a little bit blurry. You probably didn’t even think about doing it. But… it’s weird that shrinking your field of vision would help you see something better.

Plus all those eyelashes are in the way! Still, it turns out there is a reason why this action comes naturally to us. Squinting really does help bring things into focus.

And not for the reason you might think. When things look blurry, it’s often because of what optometrists call refractive error. This essentially means that your eyes are having trouble focusing light accurately on your retinas, those special layers of nervous tissue in the back of each eyeball which receive visual information and pass it along to your brain.

There are lots of reasons this can happen, but they all generally boil down to issues with the shape of your eyes. You see, when you want to see the details of something, like the fine print in a book, or text written far away, your eye muscles squeeze or relax to change the shape of your eyes ever so slightly. Specifically, they tweak the shape of your lenses—those are the curved, transparent discs toward the front of each eye.

The goal is to get the light from the object in question to fall on a special spot in your retina called the fovea, which is better equipped to resolve detail. So, you might think the point of squinting is to redirect the light that’s coming into your eye by strong-arming your lenses into the shape you need. And it does do that.

But that’s probably not why it helps you make out today’s special on the chalkboard across the room. Instead, the important thing squinting does is limit the light that reaches your pupil. This helps reduce glare, and it ensures that the light rays that enter your eye do so more directly through the center of the lens, so they’re basically already headed for that special spot.

You can actually get the same effect without moving your eye muscles at all by looking at the world through a tiny hole, like this. It actually works. I'm gonna take my glasses off.

Can I read the teleprompter? No! But closer!

If that trick doesn’t work for you, that tells you something about your vision. In fact, your eye doctor may have used a similar test when examining your eyes to narrow down if any issues you have with your sight are from refractive errors or something else. Basically, they can have you look at an eye chart with and without a pinhole occluder, and if that alone helps you read those smaller lines of text, then glasses or contacts will likely be useful to you.

You might have even seen places selling what I guess could be called “fashionable” versions of these occluders called pinhole glasses. The idea being that, hey, you don’t really need corrective lenses! You can just look at the world through some small holes.

And not only will you be able to see clearly, you could actually correct your vision problems over time. But you probably don’t want to swap your prescription for pinhole shades just yet. There isn’t actually any evidence wearing these things can fix your eyes so that you can eventually see just as well without the glasses.

And while wearing pinhole glasses can improve things like your depth of focus and the distance at which things are clearly visible, other aspects of your vision get worse. You know, things like your perception of depth and contrast and your peripheral vision. All things that are useful!

And people in studies have reported noticeable discomfort after undergoing tests with different pinhole glasses. So while it’s pretty amazing that just looking at the world through small holes can make such a big difference, it’s not really something you want to do all the time. Which is why we don’t, y’know, just squint all day long, either.

That sounds uncomfortable, and unpleasant! Thanks for asking, Janet Christian! And thanks to all our other patrons on Patreon, too.

Their support helps ensure that we here at SciShow can keep making free, good, educational science videos like this one. If you liked this video and want to consider joining our community of patrons, you can learn more at Patreon.com/SciShow. And if you’re already a patron, don’t forget about our QQ inbox!

We’re always looking for great little queries about the universe that we can answer with episodes like this one. So whenever a weird science questions that pop into your head while you’re about to fall asleep or having a boring dinner, send them to us! We might end up answering them, then we will have content, and you will have answers! ♪♪♪.