One of the most common sights almost anywhere in the world is -- eyeglasses! Since we depend so much on the lenses inside those frames to improve our view of the world, you might wonder just what goes into creating them.

In this edition of HowStuffWorks, we will talk about how the eye focuses, how a lens works, how to read a prescription, and finally, how the lens is made, including the steps involved in grinding and shaping plastic lens blanks to fit an individual's prescription and frame.

Let's start with some vision basics.