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.
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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.