Pinhole Glasses: They’ll Do in a Pinch, But Not in a Car

Has this ever happened to you?
You’re at home, polishing the silver, when the phone rings.

It’s your spouse, frantically calling from a hotel room out of town, where he’s got an important business meeting in an hour.

He’s frantic because he forgot the piece of paper that has the password he needs for his presentation. You find the piece of paper, but you can’t find your glasses. Without your glasses, the password looks like this:

He needs that password now, so you don’t have a lot of time to look for your glasses.

Don’t fret! Here’s a little trick that will let you see clearly, even if you’re nearsighted or farsighted, or have an astigmatism, and you can’t find your glasses.
Make a fist.

Good. Now hold it up to your eye.

No, don’t punch yourself in the eye – we’re not your big brother or sister playing a game of “Why Are You Hitting Yourself?”

We’ve outgrown that. Just gently close your fist and hold it up to your eye, with the thumb side of your fist closer to your face. But don’t close your fist completely. Leave a tiny opening you can look through.

Yes, that’s how you look through it, but use your fist.

Better, but your fist is too open. Pretend your fist is a telescope.

Wow, you have a great imagination! It actually looks just like you’re peering through a telescope. Now, look at the password through the little opening in your fist.

When you look through the little opening in your fist you can see the password clearly, and you can read it to your spouse, who can now ace the business meeting. You’ve saved the day, making both you and your spouse very happy.

What’s going on here – we said you’ve saved the day, making you and your spouse happy. What? They are? You mean, that’s how they … ? Oh. OK, maybe they’re a little … kinky.

Yow – they are kinky! No problem. We don’t judge. Just as long as they’re happy.

Enough about Lucy and Ricky. We’ve got some ’splainin’ to do about how this works. How can you see clearly when you look through a tiny opening in your fist? And what’s up with those “eyeglasses” that are outfitted with little pinhole openings in sheets of plastic where a normal pair of eyeglasses has lenses?

Those are called pinhole or “stenopeic” glasses. Stenopeic (pronounced “Sten-o-PEE-ic”) is a Greek word meaning “little opening.”

No, we said “little opening.” Grow up, Miley. Why can’t you act more mature, like the greatest scientist of the 20th century?

OK, never mind.
Stenopeic or pinhole glasses work by allowing only a very narrow bream of light to enter the eye through the pinholes. This reduces the size of what’s called the “blur circle” or more evocatively, the “circle of confusion.”

No, that’s not a circle of confusion. That’s a sphere of confusion. The circle of confusion refers to the blurriness you experience if your eyeball is too long, causing nearsightedness; or too short, causing farsightedness; or if your cornea is not perfectly spherical, causing astigmatism.

When your eyeball is neither too short nor too long, and your eye’s cornea is the proper spherical shape, light is refracted – i.e., bent – so that it is focused in a single pinpoint on your retina at the back of your eye.

By blocking all light in the blur circle (the circle of confusion) that doesn’t enter the pinhole, stenopeic or pinhole glasses work the way a pinhole camera works.

The light rays on the outside of the pinhole, those in the blur circle (the circle of confusion), are eliminated, mimicking the way an eye with no refractive errors focuses light onto the retina.
Here’s how it works with stenopeic or pinhole glasses:

Stenopeic or pinhole glasses are fine to use in a pinch, as in our example with Lucy and Ricky. They will provide a clearer image than you’ll get trying to see without your glasses or by squinting.

But they won’t provide an image that is as clear as what you’ll get with prescription lenses.

(She’s wearing frame 628021.)
And this should go without saying, but we’re going to say it anyway: Because these glasses only allow a tiny bit of light into the eye, they should not be used in any situation in which you need a full field of vision, especially peripheral vision, such as driving.

Also, contrary to claims made by some pinhole glasses manufacturers and wearers – which have not been subjected to rigorous scientific trials and are therefore unsupported by evidence – they will not strengthen your eyes with repeated use.

In addition, they won’t even help you in a pinch if you are strongly nearsighted, meaning that the Sphere section on your prescription for either eye is more than -6.00.

Along with stenopeic or pinhole glasses, there’s another style of non-prescription-lens glasses out there you may have seen a certain rap star wearing.

Unless you get them with sunglass lenses, these slatted glasses, which are marketed as “shades,” simply have horizontal slats going across what in sunglasses would be the lens part of an aviator-shaped frame. They can be a cute accessory, if you’re a cute accessory.

But they neither provide UV protection nor keep light out of your eye. Moreover, the horizontal slats going across what would be the lens area in a pair of prescription glasses only emphasize the horizontality of what you’re looking at.

Hmm … maybe that’s why Kanye likes them!

4 Responses

  1. Gene Gordon says:

    Another fun and informative blog, Matthew!

    I wonder if you would address two issues: 1) the Bates Method. Many, many years ago I read a book that really impressed me. Exercise your eyes, it urged – roll them around and around. Strengthen the muscles around the cornea. People who wear glasses have to go back every year or so to get stronger and stronger prescriptions, because the glasses do what the muscles should be doing and the muscles get weaker and weaker.

    2) How does excessive time at the computer – many hours every day – affect your eyes? I’m talking about a big (21.5 inch) iMac.

    • Eileen says:

      I would also find this an intersting topic. I have a friend who refuses to wear glasses, even though she desperately needs them, because she thinks glasses will weaken one’s eyes. I don’t believe this to be true.

      • Thanks for your comment, Eileen. You are correct. Wearing eyeglasses won’t harm your eyes, even if the prescription is wrong. (Eyeglasses with the wrong prescription could have other effects, such as giving you headaches, eyestrain, and nausea, not to mention making what you look at blurry.) Of course, wearing eyeglasses without 100 percent UV protection outdoors, even if it’s not sunny, could damage your eyes. That’s why every pair of glasses Zenni sells, clear as well as tinted, prescription and non-prescription has free 100 percent UV protection.

    • Thanks for your comment, Gene! To address your first question, each eye has six extra-ocular muscles that control the movements of the eye. They are not connected to the cornea. They are connected to the sclera, a protective coating which, along with the cornea, constitutes the fibrous tunic (covering).These are exercised every time we use our eyes, and don’t need to be exercised further. The changing shape of the eye and cornea as a result of aging is responsible for changing prescriptions. It has nothing to do with insufficiently exercised muscles. Regarding your second question, your vision won’t deteriorate from frequent long sessions at the computer, just like it won’t from reading at night by candlelight. However, if you are experiencing eyestrain, a 10-percent pink or amber tint on your lenses could help alleviate that, along with frequent rest breaks away from the computer.

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