– what does 20-20 vision mean?

Question

Can one have 20-40? What does it mean to have normal vision? What does the by merator and denominator mean?

In: Biology

Answer 1

The numerator is “number of feet away that you can still see details”. The denominator is “number of feet away that someone with normal vision can still see details”.

So 20/40 means “while someone with normal vision can see details from 40 feet away, **you** need to be 20 feet away to see the same details”. So your distance vision is worse than normal.