Ever wonder what it means when someone tells you that they have 20/20 vision? Is it something to boast about? You know it’s a good thing when your eye doctor tells you that you have 20/20 vision, but do you know what those numbers mean?

The numbers

Twenty what? The American Optometric Association defines 20/20 vision as normal vision acuity (the clarity and sharpness of your vision) measured at a distance of 20 feet. Normal vision at 20 feet is designated as 20/20 vision. For humans, 20/200 vision is considered poor distance vision and 20/10 vision is exceptionally good distance vision.

The eye chart

When you go to the eye doctor, your visual acuity is measured with a Snellen Chart, that white poster with the printed letters in descending sizes. Your eye doctor will ask you to read as far down on the chart as possible without squinting or visual aids. If you have 20/20 vision, that means you can clearly see and read the line that a person with “normal” vision can see when they stand 20 feet away from the chart. If you have 20/40 vision, your eyesight is slightly inferior, and you can see at twenty feet what a person with normal vision can see at 40 feet.

Your left and right eyes can have different visual acuity. Eye doctors use comprehensive eye exams to determine the corrective prescription lenses you need to be able to see with 20/20 vision.

Legal Implications

In most parts of the United States, drivers are required to have a corrected visual acuity of at least 20/40. Individuals with corrected acuity of 20/200 or worse are considered legally blind.

How good is good?

It is rare for humans to have better than 20/10 vision, while birds of prey can have acuity of 20/5 or better.

Individuals with good distance vision can have other vision problems and might benefit from corrective lenses. A complete eye test measures near vision, peripheral vision, depth perception, color perception and the ability to perceive contrast. Eye health is determined by checking eye fluid pressure, dryness, and the condition of the retinas.

Vistar Eye Center professionals can answer all your questions about eye exams. Call us today at 540-855-5100.