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