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What does a measured eye sight of 20/20 vision, or 20/40, 40/20 mean?

How do eye sight scores compare to Optometrist's Prescriptions numbers for corrective lenses?
In: Health.Ailments Asked by: r56 Nov 30, 2007 - 33 Months Ago.  Viewed 28817 times



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In the Snellen fraction 20/20, the first number represents the test distance, 20 feet. The second number represents the distance that the average eye can see the letters on a certain line of the eye chart. So, 20/20 means that the eye being tested can read the small size letter that the average person can see from 20 feet away. If a person sees 20/40, at 20 feet from the chart that person can read letters that an average person could read from 40 feet away.

As you can see, 20/20 vision is not perfect vision; it is average vision. Examples of better than average vision would include 20/15 and 20/10.
Answered by: Hatim - 33 Months Ago.
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20/10 is as good as it gets. That's when you can see from 20 feet what average person can see from 10 feet.

At 20/40 you need glasses with -0.75 prescription, which is a low prescription.

At 20/200 you need glasses with -2.00 to -2.50 prescription.
Answered by: mkrell - 32 Months Ago.
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A easy way to remember is this:

* big numbers = good vision. So 40/20 is great.

* small numbers = bad vision. So 20/200 is bad.

* By definition, 20/20 is AVERAGE.
Answered by: sherwin - 27 Months Ago.
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What does a measured eye sight of 20/20 vision, or 20/40, 40/20 mean? How do eye sight scores compare to Optometrist's Prescriptions numbers for corrective lenses? - HelpGlobe.Health.Ailments
 

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