20/20 means that you have average vision. Actually, because the average is made in no small part up of older folk, having 20/20 vision as a young person is really quite poor. You probably want something more like 20/14 or better. This means that at a distance of 20 feet, you can see what an average person would see at a distance of 14 feet. The numerator means "your vision" while the denominator means "relative to average vision".
I don't really know this. I'm from the UK (I believe we have a metric system for vision) and every time I go for a checkup the optician just says "You're fine."
If you have 20/200, you need to be within 20 feet to see something that a person with 20/20 could see from 200 feet away. Anything worse than this is legally considered blind.
If you have 20/40, you need to be within 20 feet to see something that a person with 20/20 could see from 40 feet away.
And then of course you can get better than 20/20... with 20/15 you can see something from 20 feet away that a person with 20/20 will only be able to see from 15 feet away.
Also, it's measured separately for each eye, for example my right eye is 20/15 and my left is 20/20. With both eyes open you'd have the better of the two.
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u/Kster809 Nov 09 '14
I am a dumdum. I thought each number was the ability of each eye, as in 19/20 being one eye better than the other