what exactly does 20/20 stand for? I understand it is excellent description of vision but what exactly do the numbers stand for/measure.
2007-08-17 13:26:36 · 7 answers · asked by AH SHIIII... 2 in Health ➔ Optical
It is the benchmark or standard for checking vision at 20 feet.
For example
You have 20/30 vision= What the "normal or perfect" eye can see from 30 feet away, you have to be 20 feet away to see it....
20/100 vision= what the "normal/perfect" eye can see from a whole 100 feet away, you have to be 20 feet away to see it.
20/15...a little different... The normal perfect eye has be 15 feet away to see what you can see from 20 feet away!! Better than the perfect eye!!
Wishing you 20/20 or better!
2007-08-17 13:35:59 · answer #1 · answered by W~~~Dream a Little Dream~~~P 4 · 0⤊ 0⤋
20/20 is a measure of visual acuity. Visual acuity is measured by specifying the smallest letters that can be identified correctly and the distance from the person to the letters. The size of the letters is standardized and have no more meaning than the size of a inch or yard, simply a standard size.
The top number specifies the distance at which the test was conducted. The bottom letter specifies the size of letter. The "20" standard letter is a letter that is 5 degrees of arc at 20 ft (about 3/4 in), the "30" letter is 5 degrees of arc at 30 ft, the "15" letter is 5 degrees of arc at 15 ft and so on.
So 20/20 means the vision was tested at 20 ft and the "20" letter was the smallest letter seen. Most people without eye disease will have vision of 20/20 or better.
2007-08-17 15:14:35 · answer #2 · answered by Judy B 7 · 1⤊ 0⤋
It is a ratio of distance. Someone who has 20/20 vision has perfect sight. If their vision is 20/80, that means, what I can see 80 feet away, they can not see it until they are 20 feet away.
2007-08-17 13:37:40 · answer #3 · answered by Kevin H 7 · 0⤊ 0⤋
It basically means that you can see certain sized letters (I am using letters as an example)clearly at a distance of 20 feet. If you go further than 20 feet you would have to use larger letters because they would naturally get smaller at a distance.
2007-08-17 13:33:53 · answer #4 · answered by lost in a world of confusion 4 · 0⤊ 0⤋
20/20 is the normal vision for a human being. Here's a weblink.
2007-08-17 13:41:58 · answer #5 · answered by cidyah 7 · 0⤊ 0⤋
20/20 means something you should be able to see from 20 feet away, you can. for example, my right eye has 20/15 vision so something you should only be able to see from 15 feet away, i can see from 20. my left eye on the other hand is 20/450. so something you should be able to see from 450 feet away, i can only see from 20. ya it sucks!
2007-08-17 18:44:03 · answer #6 · answered by funkykomadina 2 · 0⤊ 0⤋
You can see clearly at twenty feet.
2007-08-17 14:22:19 · answer #7 · answered by Mrs. Arrow 2 · 0⤊ 1⤋