Eye and Vision

What is normal vision?

A Answers (1)

  • ADiscovery Health answered

    Vision (also called visual acuity) is tested by reading an eye chart at a distance of 20 feet. By examining many people, eye doctors have decided what a "normal" human should be able to see when standing 20 feet from an eye chart.

    If someone has 20/20 vision, that means he can stand 20 feet from the chart and can see what a "normal" human sees. Therefore, if someone has 20/20 vision his vision is "normal" - a majority of people can see what he can see at 20 feet.

    If someone has 20/40 vision that means when she stands 20 feet from the chart she can only see what a normal human can see if standing 40 feet from the chart. In other words, if a person with "normal" vision stands 40 feet away from a chart, and a person with 20/40 vision stands only 20 feet from the chart, both can see the same detail.

    Likewise, 20/200 means that when a person stands 20 feet from a chart he can only see what a normal person standing 200 feet away can see. The cutoff for legal blindness in the United States is 20/200.

    It also is possible to have vision better than normal. A person tested to have 20/10 vision can see at 20 feet what a person with normal vision can see when standing 10 feet from the chart.

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.
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