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The numbers used to measure vision are probably some of the most recognizable in the world. 20/20 has become shorthand for seeing things clearly, not just physically but metaphorically, too. But what do those numbers actually mean?

The answer is actually fairly simple. These numbers measure your visual acuity, so if you have 20/20 vision, you can clearly see at 20 feet what normally should be seen at that distance, according to the American Optometric Association (AOA). If you have 20/40 vision, you can clearly see at 20 feet what a person with normal vision can see at 40 feet, if your vision is 20/100, you can clearly see at 20 feet what a person with normal vision can see at 100 feet, and so on.

However, having 20/20 vision doesn’t necessarily mean you have perfect vision, the AOA states. It just indicates sharpness or clarity of vision. Peripheral vision, depth perception, eye coordination, color vision, and focusing are also factors in measuring the quality of your vision.

Visual acuity is measured by reading a Snellen Eye Chart. Those are the charts with 11 rows of letters, decreasing in size and usually starting with a large E, hanging in your eye doctor’s exam room. The largest letter on this chart represents visual acuity of 20/200. If that is the best you can read with corrective lenses, you are considered legally blind. Conversely, the AOA states, if you can read past the eighth line – which is 20/20 – your vision could be 20/15, 20/10, or even 20/5. Few people have visual acuity 20/10 or better, though many animals do.

Whatever your visual acuity, though, the meaning of these numbers is now clear to you.

This blog is for informational purposes only. For specific medical questions, please consult your physician. If you would like to see if you have 20/20 vision and get a complete eye examination, call 704-295-3000 to set up an appointment with a CEENTA ophthalmologist. After your appointment you can get a new set of glasses at one of our optical shops.


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