When people refer to 20/20 vision, what exactly does this mean?

Question

What is "20" for, and how is a better or worse number determined(I know vision quality makes it higher or lower on the other side, but where do they get the numbers from?). Why is it called 20/something. Who made this system up? What scientific evidence is there behind it that says this is our accurate vision standard?

Just wondering....

Answer 1

This confusing reference works like this: 20/20 is what the normal person can see at 20 ft. The higher the second number, the worse the vision. Like 20/50 means a person would have to move to 20 ft to see what the normal person could see at 50 ft. The standard eye chart was developed using a system that measures how well a person can differentiate between two lines at a measured distance. Most eye charts have to be at, at least, 20 ft to be accurate.

Answer 2

perfect n normal vision

Answer 3

basically it means that you have perfect vision =). grrr and im a blind one...lol

Answer 4

It means the person has perfect vision and can see very well.

Answer 5

Someone with 20/20 vision can see from 20 feet away what an average person can see from 20 feet away. Someone with 20/16 vision can see from 20 feet away what the average person can see from 16 feet away. Someone with 20/80 vision can only see from 20 feet away what the average person can see from 80 feet away. Make sense?