Here is an explanation of 20 20 vision.
“20/20” is the common expression used in the United States for a normal level of vision.
(In the UK the standard is 6 metres and it is called 6/6 vision.)
By the results achieved by what lots of people can see at 20 feet from an eye chart, eye care professionals have decided what is normal vision for a human.
That means if you have 20/20 vision you can see what a normal person can see at 20 feet from an eye test chart.
If you have 20/40 vision this means that at 20 feet from an eye test chart you can see what a person with normal vision can see at 40 feet meaning you have a poorer level of vision than a normal person.
Whereas if you have 20/15 vision this means you can see at 20 feet what a normal person can see only at 15 feet and hence you have better than normal vision.
20/ 20 does not mean perfect eyesight!
That is right! Please understand and remember remember that 20/20 does not necessarily mean perfect eyesight.
What do I mean?
Consider this carefully:
Since the test which your optometrist records as 20/20 on an eye chart measures only your visual acuity and not the other eye vision conditions, you may have 20/20 eyesight and still have problems with your vision.
For example, with 20/20 eyesight you might have difficulty seeing near objects. Or you may have difficulty reading. What else? Perhaps also reduced depth perception, problems focusing, or reduced peripheral vision.
Each eye is normally tested separately and then both eyes together to record vision binocularly.
Nearly all patients who undergo an eye examination will have slight differences in their visual acuity between the two eyes.