WHY do some people wear glasses?
If your eye is not exactly the right shape or your lens cannot focus correctly, you will not create a clear image on your retina.
When this happens you have to wear glasses. As we grow older, the lenses in our eyes become harder and are not able to change shape to focus on things close to us.
This is why we become longsighted (finding it hard to see objects that are close) as we get older. - Tell Me Why?, Chancellor Press