How bad does your prescription have to be when you can't where contacts anymore?

Question

How bad does your prescription have to be when you can't where contacts anymore?

Answer 1

In terms of + or - power? -20 or +20 is the maximum. Translation: Pretty d**n High.

Answer 2

If your vision can be corrected with glasses, there is a 99% chance that contacts will do it also.

Contacts are available in any prescription that glasses are.

There are certain conditions where contacts won't work of course, but not because of the prescription being too strong.