What Is 20/20 Vision?

Almost everyone has heard of the numbers 20/20 when it comes to vision.  There’s even a commonly quoted phrase “hindsight is 20/20”.  But what is 20/20?  What does that even mean?

How Vision Values Like “20/20” Are Measured

Well, it’s really not as complicated as it seems.  The numbers are referring to a distance of 20 feet.  For our friends in countries using the metric system, you’ll see 6/6, which is referring to 6 meters.  Either way, the concept is the same.  

The top number is referring to what your eye is seeing at a 20 foot distance while the bottom number is referring to what a “normal” eye should see at a 20 foot distance.  It becomes easier to make sense of that when we start changing the numbers.  

Example: How Vision Measurements Compare

For example, if you were told your vision is 20/40, that means you need to be standing 20 feet away from the target to see what a “normal” eye would be able to see from a 40 foot distance. 

Imagine you’re on the sidewalk with a friend and you’re 40 feet away from a street sign.  Your friend, who has very good vision, can read that the sign says “Main Street”. You forgot to bring your glasses with you, so you can’t quite read it until you get a little closer. You start being able to read it at 20 feet away.  

That means, without glasses, you have 20/40 vision, which happens to be the minimum level of vision that is required for driving in most states.  Someone that is 20/50 or worse would be required to wear glasses to drive.  

So the 20/20 numbers are really just a ratio comparing your vision to a normal, or standard, level of vision.

My Doctor Said I’m 20/400 Without My Glasses.  Am I legally blind?

Well, not exactly.  For people with higher prescriptions (i.e. thicker glasses) that cannot see much without them, they may feel “blind”, but if they see well when their glasses are on, then they are not legally blind.  

As a reminder, 20/400, which is often “the big E” on the eye chart at the eye doctor’s office, is referring to the ratio of your eye seeing that letter E from a 20 foot distance even though a “normal” eye would be able to see it from 400 feet away.  

Legal blindness, in most places, refers to 20/200 or worse vision even while using your best vision correcting glasses or contacts.

Does 20/20 Mean Perfect Vision?

Well, pretty close, but most healthy, normal eyes can usually see just a little better than 20/20. 

What is Better than 20/20 Vision?  

You guessed it: 20/15, or even 20/10.  It’s not uncommon for people to easily read letters on the 20/15 line of the eye chart.  20/10 level of vision is much less common, but still possible.

Interestingly, military fighter pilots often are able to read 20/10 letters on the eye chart.

“Eagle-eyes”

If you’re one of the lucky ones with excellent vision, you may have been nicknamed “eagle-eyes” at some point and most likely beamed with pride upon hearing it. 

However, if we’re comparing our eyes to an actual eagle, there’s no contest.  Eagles not only have a much wider peripheral field of view than humans, but also have a much better resolution than we do.  

In terms of 20/20 numbers, an eagle’s vision is estimated to be 20/5, or maybe even slightly better. That’s twice as good as our best fighter pilots!  On top of that, they see colors much more vividly than we do, and even see colors that we cannot see. 

Not Sure What Your Vision Numbers Are?

Schedule an eye exam with your eye doctor and they can easily let you know what your vision measurements are.  

Not only that, if needed they can give you a prescription for glasses and/or contact lenses to optimally correct your vision and hopefully get you seeing 20/20 or better.