If you’re ever stranded on a desert island and you break your glasses, hey, don’t worry. You can make pinhole glasses out of some bark or the skin of an animal you trapped or something, and then you will be able to see. Just take something opaque, and poke a slit or a bunch of small pinholes in it over where your eyes would be.
Where ideally-shaped corneas or corrective lenses would ordinarily adjust the angle of incoming light rays and focus them into a sharp image, the pinholes will instead physically block the entrance of all light rays that were coming into your eyes on a blur-creating angle, allowing in only the rays that are already ideally focused. Think of these pinholes as an extreme version of squinting. Ta da!
You can get the same effect with your hands, too, if you put them like this and then wear them like glasses (works best with even smaller eyeholes- try to get them pinhole sized):
Even if you have good vision, you’ll probably be able to see an increase in sharpness if you peer through a tiny pinhole. Apparently those Inuit snow goggles with the slits will also have this effect, although I can’t say for sure since I avoid snow like it was asking me to smell its finger.
I learned this (and borrowed the photos) from a very practical website called Karen’s How-to Page. She also has ideas for making hiking gear, like a hat or cape, and how to turn your hands into a sundial, and other stuff that is soooo practical it made me do this face: O_o
PS – If you like practical hacky stuff like this, check out my tutorial: How to Unclog a Drain without Chemicals. I have a cloud of hair that could jam a weed whacker, so you know I’m an expert in this stuff.