How do glasses help us see better?

Question: How do glasses help us see better?
- Keywords:
  blind,
  glasses,
  lens,
  sight,
  vision
Asked by hannahbanana to Steve on 17 Mar 2011.
- Stephen Moss answered on 17 Mar 2011:
  
  Hi Hanna
  
  When we see things, the light from those things is focused by the lens in our eye on the specialised light sensing cells (the retina) at the back of the eye. But if the lens doesn’t work properly then the focusing does awry and the world appears fuzzy. This happens to almost all of us as we get older. The good thing about glasses, and people discovered this hundreds of years ago, is that by simply placing a curved lens in front of your own eye, you can correct the problem and see the world in focus again. The thickness of the glasses you need will depend on how well your own lens works.

Question: How do glasses help us see better?