What Does 20/20 Really Mean?

chart used in an eye checkup Manhattan NYFor many people, 20/20 vision is the epitome of visual acuity and is the proclamation they would love to hear from their optometrist. However, very few people know the real meaning of 20/20 vision. Below is some more information on this topic.

An Overview Of Visual Acuity Testing

Across the US, vision testing is based on the Snellen chart. It consists of alphabetical letters that grow progressively smaller with each new line. Herman Snellen, a Dutch ophthalmologist, developed the Snellen chart way back in 1862. It has since become the most common standard for testing visual acuity worldwide. Individuals undergoing vision testing are required to stand at least 20 feet from the Snellen chart and read the letters on the chart. They start with the largest letter at the top and then go down the chart.

It is important to note that you will be declared legally blind if you can only see the biggest letter on the Snellen chart with the help of corrective lenses. On the other hand, the ability to see the largest letter with the naked eye translates to 20/20 visual acuity. This fraction-based visual acuity measurement gets larger as the letters on each line grow increasingly smaller. The smallest letters on most Snellen charts correspond to visual acuity of 20/10. You may also come across Snellen charts where the smallest letters translate to 20/15 visual acuity. In general, the eyesight of a person with 20/10 visual acuity is as twice as sharp as the eyesight of a person with 20/20 vision. To become a fighter pilot in the US military, you must have 20/20 vision or better. All US states require drivers to have at least 20/40 vision.

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Why 20/20 Vision Is Not Necessarily Perfect Vision

There are several reasons why 20/20 visual acuity does not translate to perfect vision. Firstly, vision-testing using the Snellen chart does not determine one’s ability to see colored letters or objects. Secondly, this type of vision testing does not determine the ability to see and differentiate moving objects. At the same time, most Snellen charts have a visual acuity rating (20/10 or 20/15) that is better than 20/20 vision as stated in the paragraph above.

What’s more, visual acuity also varies depending on factors such as lighting, eye care, color depth perception and contrast sensitivity. As such, one can have visual acuity that is better than 20/20. This also means it is practically impossible to define what constitutes perfect eyesight or not. Nevertheless,procedures such as surgery can improve visual acuity significantly for people with visual problems. This is also true for people diagnosed with serious vision conditions that cannot be resolved with normal eyeglasses or contact lenses. The best way to determine your visual acuity is by undergoing a thorough eye exam at a qualified optometrist’s office.



Contrary to popular belief, 20/20 vision does not correspond to perfect vision. This is because visual acuity is a function of multiple factors including color vision, contrast sensitivity, depth perception, and eye focusing speed. In addition, most Snellen charts have a visual acuity rating that is better than 20/20 vision.

Eye Checkup Manhattan NY

A major component to keeping your eyes healthy is by getting a comprehensive eye exam by reputable optometrist. This will ensure that your eyes stay healthy and that you will receive treatment for any eye health issues that you might be experiencing.

Schedule an eye exam today in Manhattan NY. Our staff is friendly, positive and professional. We are committed to providing each patient with quality vision solutions.

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Call us today at (646) 863-1997 or contact us for any questions that you might have on your eye care needs!

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