TL;DR? Make a tiny hole with your hand

April 28, 2014 6:46 AM

How To See Without Glasses

(Minute Physics - previously)

posted by gwint (37 comments total)

The cost of this, of course, is that everything is dim. However, before I looked into laser with remaining eyeball, it was a great way to check what time it was when I woke up in the middle of the night.
posted by eriko at 6:48 AM on April 28, 2014 [3 favorites]

Oh, and you look like a bit of a fool. Bonus, that.
posted by eriko at 6:49 AM on April 28, 2014 [3 favorites]

This is what my father in law has to do when he wants to read. Incidentally, he's also a champion rifle marksman (perhaps ironicly using "peep sights") so go figure.
posted by The 10th Regiment of Foot at 6:54 AM on April 28, 2014

I remember something we did in school or something with a piece of paper and a pin hole that did the same trick.
posted by xingcat at 6:56 AM on April 28, 2014 [1 favorite]

Opticians hate him!
posted by thelonius at 6:57 AM on April 28, 2014 [25 favorites]

As a nearsighted kid in 8th grade, who had a teacher that wrote test questions on the chalk board, I discovered this one as well... It worked until my folks could afford glasses for me!
posted by newfers at 6:57 AM on April 28, 2014

Not new to anyone who played around with pinhole cameras as a kid...
posted by Decani at 7:00 AM on April 28, 2014 [2 favorites]

Does not work for me. I mean, I can change how blurry things are, but I can't make it unblurry. I can't read the screen while sitting in front of it without leaning a lot closer.
posted by Foosnark at 7:12 AM on April 28, 2014

I do it all the time in the middle of the night when I need to see the time without grabbing my glasses. It works great.
posted by lydhre at 7:16 AM on April 28, 2014 [1 favorite]

Relevant
posted by Zalzidrax at 7:18 AM on April 28, 2014 [10 favorites]

I'm in love with this. Seriously.

As for looking like a dork, I'm a dad and a software engineer, so Pandora unlocked that achievement a long time ago.

Interestingly enough, one of my brothers has vision that his eye doctor said would have made him sought after in the Medieval period. He is far sighted in one eye and near sighted in the other, so he can see up close by covering one eye and far away by uncovering that one and covering the other. I could see that useful as an architect or surveyor.
posted by plinth at 7:22 AM on April 28, 2014 [2 favorites]

Well, it kind of works for me. I have to close my fingers so tight as to barely be able to fit a pin through, and then I have to crush the opening super tight against my head. As I do it on this page right now, I can kind of see only one or two words at a time. My eyes are shit.

Handy, I suppose. I'm trying real hard to figure out when I'd ever have to use this.
posted by Thorzdad at 7:26 AM on April 28, 2014

Independent of the usefulness of the trick, I thought the video was great, especially the diagrams. Just a little bit of motion in a diagram can really help communicate an idea.
posted by samw at 7:30 AM on April 28, 2014 [1 favorite]

If you're nearsighted, as I am, you can also physically change the shape of your lens by pressing (gently), on your top and bottom eyelids. This is best noticed by closing one eye. The image isn't perfect as you are, after all, altering the shape of your lens.
posted by herrdoktor at 7:31 AM on April 28, 2014 [2 favorites]

He is far sighted in one eye and near sighted in the other

I enjoy the same effect but mine came from cataract surgery on both eyes. My insurance wouldn't spring for variable focus implants so my surgeon suggested this so I wouldn't need to use glasses for anything. It's amazing how quickly the brain adapts. Within a day or two I was unconsciously shifting from eye to eye as needed and it's never bothered me...
posted by jim in austin at 7:33 AM on April 28, 2014 [1 favorite]

It's amazing how quickly the brain adapts. Within a day or two I was unconsciously shifting from eye to eye as needed and it's never bothered me...

My optometrist set me up with contacts like that last year -- my left eye is adjusted for close vision, my right for far -- to keep me from having to get progressive contacts (which I assume are way more expensive). He said about 80% of people can adapt to it; I think it took me less than a day. My glasses, otoh, are not set up like that -- they're progressive, with close vision at the bottom and far vision at the top. I don't have even a second's disorientation when I switch between contacts and glasses, despite using two completely different forms of vision adjustment.

The brain is an amazing thing.
posted by current resident at 7:46 AM on April 28, 2014 [1 favorite]

Huh, I never thought to try this even though I've got a PhD in optics and terrible vision. Works really well!

I have been told, though, that this is at least partly why squinting at things helps -- smaller aperature. (As well as maybe a little extra muscle pressure on the lens of your eye?)

Now these guys should make a video teaching people how to sense polarization with their bare eyes via Haidinger's brush.

Easiest to learn with a polarizer (like one lens of a pair of polarizing sunglasses) and a uniformly illuminated bright white wall. Rotate the polarizer and the "brush" rotates.

But once you know what you're looking for, you can see it on a white LCD screen -- or a clear blue sky -- without the polarizing lens.
posted by OnceUponATime at 7:48 AM on April 28, 2014 [2 favorites]

I discovered this at some point around 4th or 5th grade when I was without my glasses for a few days for some reason. It did enable me to read the blackboard well enough to get by, until a teacher demanded to know what I was doing and mocked me mercilessly for thinking something so ridiculous would work. (I didn't think, I knew but I was just a kid so I couldn't possibly know.) I was forbidden to continue doing it and so spent a couple days totally confused in class until I got my glasses back.
posted by pbrim at 7:49 AM on April 28, 2014 [1 favorite]

My vision has gotten worse, I guess. I remember testing this out in middle school or so, and it worked ok then (although I had incorrectly been told it was due to diffraction-- can't be, diffraction effect sets in with a much smaller hole, approx. width of a human hair).

But now my hand just can't make a small enough hole for all of the light in it to be focused. Stupid long eyeballs. (I happened to be sewing and sew checked with a nearby piece of paper and a small pin prick-- that still works).

Also the main application for this for me is "where the heck are my glasses"-- and since it by nature gives a small field of view, it's not exactly practical.
posted by nat at 7:51 AM on April 28, 2014

I believe this is also why as a kid you were somewhat shocked that playing spyglass with the cardboard at the center of a paper towel roll kind of worked for realsies.
posted by Muddler at 7:57 AM on April 28, 2014

I discovered this principle on my own when I was around 8 years old (when I first started to go near-sighted). My method involved both hands (pushing both thumbs and forefingers together to make a little aperture in the middle of the four digits). My dad saw me doing this and said "I see what you're doing there; I used to do the same thing before I got glasses, but like this" (demonstrating the one-hand version like in the video). I was amazed (and sort of still am). Anyway, I think he told my mom, because I was in glasses a couple of weeks after that!

But this is the first time I've ever seen an explanation of the physics behind it, so great post!
posted by JimInLoganSquare at 8:00 AM on April 28, 2014 [1 favorite]

Neat! This is how I see the clock in the morning. (I'm so myopic that when my current optometrist asked me to look at the eye chart during my first visit, I had to sigh and point out that not only did I see nothing on the eye chart, I couldn't even see that there was an eye chart. I'm wearing progressive contacts even as I type.)
posted by thomas j wise at 8:21 AM on April 28, 2014

When I wore glasses, I was so nearsighted that this trick barely worked. I could see it being practical for those with mild myopia, though.
posted by Dip Flash at 8:25 AM on April 28, 2014

You can also look through a Saltine cracker. Remove the oyster and hot sauce first.
posted by RobotVoodooPower at 8:26 AM on April 28, 2014 [3 favorites]

I'm always surprised when nearsighted people don't know this. I don't know how I figured it out, but I must have been pretty young. Much too young to understand why, but also much too young to care.
posted by still_wears_a_hat at 8:27 AM on April 28, 2014

I have terrible nearsightedness plus astigmatism and glaucoma and am old enough that I now have to have progressive (bifocal) lenses. Recently I've had a dry eyes/blurry vision thing where I cannot even watch TV unless I'm 3 feet away, and the doctor had problems dialing in a new prescription that gave me sharp vision. But they have a black plastic thing you hold over one eye at a time (glasses on) for some of the tests. At some point they flipped down a little flap and said "does that help?" and it was like OH MY GOD I HAVE CRISP 20/20 OR BETTER VISION FOR THE FIRST TIME IN 10 YEARS YES THAT'S IT. Turns out the flip-down thing is just black plastic filled with pinprick holes.

Hopefully my new glasses will work as well but I briefly considered just wearing the pinprick cover all the time like some kind of weird goggles. Too bad they can't add that feature to lenses somehow ...
posted by freecellwizard at 8:44 AM on April 28, 2014

If you're nearsighted, as I am, you can also physically change the shape of your lens by pressing (gently), on your top and bottom eyelids. This is best noticed by closing one eye. The image isn't perfect as you are, after all, altering the shape of your lens.

Huh! I knew about the pinhole method (and why it works) but I'm sufficiently nearsighted that I can only see such a small part of the floor once I've got the hole small enough that it's quicker to go fairly-blind by memory to grab my spare pair, when a cat knocks my main pair under the bed or somesuch.

The pressing-gently-on-the-eyeball method though works a damn treat in comparison, and also gives me a vague inkling of what it must be like to have lasek-corrected vision. Thanks!
posted by ArkhanJG at 8:46 AM on April 28, 2014

I've been doing this since I was a kid.
posted by jeff-o-matic at 9:00 AM on April 28, 2014 [1 favorite]

For people with macular degeneration, an artificial lens (implanted behind the iris) has been developed that has a small telescope that (if I'm remembering correctly) fits into your pupil. The idea is to magnify the image in one eye 2 or 3 times so the part of the image that was most affected by the damaged part of the retina will be large enough to fall onto healthy tissue. The brain then combines the remaining peripheral vision of one eye with the now magnifed image of the other.

I don't know if it's moved beyond testing but apparently people have a lot more trouble adjusting to whatever kind of image that produces than having one eye for near and the other for distance.
posted by AtoBtoA at 9:01 AM on April 28, 2014 [1 favorite]

Ok, that's really cool. It really works. Except that all I can see is one word at a time...
posted by leahwrenn at 10:03 AM on April 28, 2014

I've been doing this for 10 years or so, and it's very handy if glasses are not in reach. However, arthritis symptoms are now starting to kick in and it's harder to get me finger that tight.
posted by MtDewd at 11:03 AM on April 28, 2014 [1 favorite]

although I had incorrectly been told it was due to diffraction-- can't be, diffraction effect sets in with a much smaller hole, approx. width of a human hair

Diffraction is what limits your ability to approach perfect resolution by making the hole smaller and smaller. Once you approach the "human hair" scale (which is getting close to the wavelength of visible light), the "ray" approximation shown in the video is no good, and you really have to start thinking of light as a wave, which introduces a sort of fundamental blurriness.

(Personally, I interpret quantum mechanics as saying that really everything is a wave, and the "uncertainty principle" as just another example of that fundamental blurriness associated with waves.)
posted by OnceUponATime at 11:20 AM on April 28, 2014

Pinhole glasses.
posted by fings at 1:26 PM on April 28, 2014

Doubly effective when done while singing the Junior Birdman theme song.
posted by skyscraper at 1:54 PM on April 28, 2014

Now these guys should make a video teaching people how to sense polarization with their bare eyes via Haidinger's brush.

Ever since I learned of this, I see it all the time on LCD monitors. It also jumps out at me if I rotate my phone.

Deliberately teaching someone of Haidinger's brush is More Cowbell or The FedEx Arrow times a million.
posted by Hatashran at 2:40 PM on April 28, 2014

This is actually a combat technique similar to this one. You have to be careful when using it to look at someone, or you could end up accidentally strangling them.
posted by homunculus at 12:15 AM on April 29, 2014

Of course, if you make the hole too small, you'll start to get a blurred image again, because of Heisenberg's Uncertainty Principle.
posted by straight at 2:43 AM on April 29, 2014 [1 favorite]