20/20: What These Numbers Actually Mean

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Everyone knows that 20/20 vision means that your sight is, more or less, perfect; and most people know that a higher second number means that your vision is worse. But what do those numbers actually mean? As it turns out, very few of our clients actually know where these numbers come from, so we’d like to explain them to you.

What It Means

Believe it or not, those numbers refer to feet, and they set a standard for people’s vision. The standard basically states that a person should be able to read a certain line of text from 20 feet away. If you can, in actuality, read that line of text from 20 feet away, then you have 20/20 vision–the distance you can read the text from, over the distance you should be able to read the text from.

Other lines of text are expected to be readable at different distances; these are the different lines of text that your optometrist may make you read during a vision test. If you are 20 feet away and can read the text that should be legible only from 15 feet away, then you have 20/15 vision. However, if you have to be 20 feet away from text that should be legible from 80 feet away, you have 20/80 vision.

How It’s Used

Optometrists use these numbers to help determine how much of an adjustment you need in order to have what is considered “perfect” vision. They may have you look through different lenses until you are able to see from 20 feet what you should be able to see. This will determine your prescription.

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