How do contact lenses work?

Question: How do contact lenses work?
- Keywords:
  eye,
  lense,
  vision
Asked by Zealousy to Rebecca on 19 Jun 2015.
- Rebecca Dewey answered on 19 Jun 2015:
  
  Short or long eyesight is usually due to the distance from the lens to the retina and the thickness of the lens, being incorrect for each other. Contact lenses work in a very similar way to glasses. The plastic is curved in a way that the light is focussed inward, or defocussed outward (depending on your prescription). Then when the light reaches your eye it is then at the right amount of focus / defocus so that your eyeball can focus the light properly into an image on the retina. The contact lens just does this from a lot nearer the eyeball!
  
  You can also get contact lenses that correct astigmatism in the same way as glasses!

Question: How do contact lenses work?