# What does it mean to have 20/20 vision?

By looking at many people, eye doctors have decided what a "normal" person should be able to see when standing 20 feet from an eye chart. If you have 20/20 vision, that means you can stand 20 feet from the chart and can see what a "normal" person can see. In other words, your vision is "normal.

If you have 20/40 vision that means you can stand 20 feet from a chart and can see what a normal person sees when standing 40 feet from the chart. In other words, if a normal person stands 40 feet from a chart and you stand only 20 feet from it, you and the normal person see the same detail. Likewise, 20/100 vision means that when you stand 20 feet away from a chart you can only see details a normal person would see standing 100 feet away. The cutoff for legal blindness in the United States is 20/200.

It is also possible to have vision that is better than normal. Someone with 20/10 vision can see at 20 feet the same detail a normal person can see if standing only 10 feet from the chart.

20/20 vision is the term used to describe the normal clarity and sharpness of vision at a distance. While standing 20 feet away, a person with normal vision would see what would normally be seen at that distance.
Ophthalmology
If you have 20/20 vision -- considered the standard for normal -- that means you can see at a distance of 20 feet what another individual with normal vision sees at 20 feet. However, if your vision is 20/40, you see at a distance of 20 feet what a person with normal vision would be able to see at 40 feet; in other words, you need to stand closer to the object to see it as clearly. In general, the higher the second number, the worse your vision.
Visual acuity is measured as 20/x, where the first 20 refers to the standardized distance in feet a patient stands from an eye chart (usually a Snellen eye chart). People with normal vision should be able to distinguish letters on the chart as small as a certain size. Someone with poorer vision would only be able to distinguish letters (at a distance of 20 feet) that someone with normal vision would be able to distinguish at a greater distance (for example, 40 feet). That person would be described as having 20/40 vision. Having 20/20 vision means that a person can see things at a distance of 20 feet as well as a person with normal vision would be able to see at 20 feet.

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