What does the second 20 in 20/20 vision mean? My coworkers and i are stumped!
In: Biology
20/20 vision is perfect vision, therefore you need to be 20 feet away from something to see it with the clarity that a normal eye (i.e. your eye) would see at 20 feet. With 20/30 vision you would need to be 20 feet away to see what a normal eye sees at 30 feet. So the first number is what the scale is calibrated for, either 10 or 20 feet. The second number is how far someone with perfect vision could see with the same clarity. The higher the second number the worse the vision.
It’s pretty simple….the first number is a static measurement of your vision…”At 20 feet away you can read letters most people can”, the second number is a comparison to “average” vision…”from 20 feet away”.
So 20/15 would mean “At 20 feet away, you can read letters most people can from 15 feet away” – this means your vision is *better* than average, being able to see letters from 20 feet away that the average person must walk a little closer (to 15 feet) to see.
Something like 20/30 would mean “At 20 feet away, you can read letters most people can from 30 feet away” – opposite of above this means your vision is worse than average, you have to be 20 feet from letters that the average person can see 30 feet away.
One twenty is the size of the font, the other is the distance in feet. Don’t remember which is which
The first 20 is what your vision is, the second 20 is what the standard, “average” vision is.
A Patient taking a vision test who gets 20/20 can clearly see an object at 20 feet that a person with average vision would see at 20 feet.
If it were 20/40, that means that the Patient has to stand 20 feet away from an object to see something that a person with average vision can see at 40 feet.
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