A Girl and her Glasses
Everyone's face is different. Some people have a round face, some people have an oblong face. The same is true with your eyes. The problem is, only one kind of eyeball works correctly, round! Like a ping pong ball. Light enters your eye, and is focused on the back of it by a little lens that is located inside your eye. Most people with normal vision can see from about one foot away to 1000 feet away. People who are nearsighted have eyeballs that are oblong, kind of shaped a bit like an egg. The back of the eye is too far away for the lens to focus correctly on it. We can see things that are real close because our range of vision is from about one inch to two feet. That's why they call it "Near" sighted. To fix this, we add a lens to the front of the eye... Glasses!
If you ever look at a pair of glasses that is worn by someone who is nearsighted, the lenses make everything look small. This "tricks" the eye, by making objects seem small and close up, which we can see just fine. These funny lenses are called "concave" because the center of the lens is thinner than the outside, just the opposite of a magnifying glass. Because the center can only get so thin, the outside of the lens can get quite thick if you are very nearsighted, thus the "coke bottle" comments! Originally, the lenses in glasses were made of glass, thus the name. Glass works really good at bending the light, in fact, a lot better than the plastic lenses used now. Also, glass is very scratch resistant (which is why I stuck with it). But, glass has two problems. One, it's heavy! This makes for a sore nose, believe me! Two, it's glass! Which means, if you happen to drop your glasses on a hard surface, Ka-Bush! There go the lenses! Most newer glasses use plastic lenses. For a few years, this was not too cool because the lenses had to be twice as thick to bend the light. Talk about your coke bottles! However, they now have high-refraction plastic lenses that work almost as well as glass.
Nowadays, a lot of people wear contact lenses. That's fine if you don't mind sticking something in your eye. (Personally, I do, thus the glasses!) They work the same way, but the lenses can be small because they go right on the eye. The lenses are made out of a soft, jelly-like plastic, which kind of reminds me of little jellyfish! People who are really into their looks prefer contacts to glasses.