How do glasses correct your vision? I know it has something to do with the retina but what exactly does it do?
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You may recall from sr. elementary school or early high school, some diagram that shows light rays coming in one side of a lens. And how due to _refraction_ (the boundary between two different materials causing light to bend its direction), a properly shaped lens can focus light to a point? [A diagram like this.](https://cdn4.explainthatstuff.com/convexlens.gif)
Well, your eyeball works pretty much the same way. Instead of film or a chip sensor like in a camera, the thing that registers or records the image is your retina at the back of your eye. [So the lens and shape of your eyeball focuses light coming in so it hits your retina just right.](https://static.sciencelearn.org.nz/images/images/000/000/053/original/Eye-focus-final-3000X2000.jpg?1522292099)
Now, as your body grows and ages, sometimes the shape of your eyeball shape goes wonky, and the image isn’t focused on your retina quite as well as it used to. Or maybe you find yourself squinting – squinting smushes your eyeball so it’s closer to the right shape. So an optometrist, using various optical tools (but really they’re all just lenses) like the Photoroptor (“which is better, A… or B?”) can determine what type and shape of lens you need that will focus the light perfectly on your retinas.
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