Here’s some free advice if you ever find yourself in a post-apocalyptic world and need glasses: squint. Because after watching How to Make Everything attempt to make a pair of prescription eyeglasses, let me tell you, it’s going to really, really hard for you to actually make a pair yourself. There are just so many materials and so many steps and so many places where things can go wrong that getting a lens that’s clear enough and that is shaped to what your eyeballs needs that it seems impossible.
First, to make glass you’d need silica, potash, and lime. Many of those materials you can just grab from sand on a beach, but if you forget to filter out something or miss a step, you end up with glass that isn't clear - meaning you have to start all over again. But let’s say you got the glass down okay, you still have to shape the lenses into your correct prescription, which means measuring the focal length. That means shaping the lens, polishing it, then using a laser pointer, a ruler, a lot of guess work, before shaping and polishing it again, some hope that you didn’t grind too much, and... yeah, just squint.
It’s still a fun exercise though, so watch How to Make Everything try to pull it off in the video below: