Your Mom may have used this line on you when you were a little kid and she was trying to get you to eat your cooked carrots. “So and so has 20/20 vision. I guess he must have eaten his carrots.”
But what is 20/20 vision? The American Optometric Association says the term is “used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet.” People with 20/20 vision can see objects, type, etc. that should normally be seen at that distance. The back number is the one that really counts. So, if your vision is 20/100, you need to be at 20 feet to see what a person with 20/20 vision can see at 100 feet.
Since 20/20 is the gold standard of vision terms, it must mean perfect vision, right? Not necessarily. 20/20 is only an indicator of sharpness or vision clarity at a distance. It doesn’t take into account other important factors of vision — peripheral awareness (otherwise known as side vision), eye coordination, depth perception, focusing ability, and color vision. A person could have 20/20 eyesight but be colorblind.
A farsighted person may be able to see the eye chart just fine. But ask that person to read the scorecard after a round of golf, and he’ll be reaching for his reading glasses. Or the person may be able to see fine at distance but is unable to focus properly (presbyopia).
So, while you may be 20/40 and your friend is bragging about his 20/20 sight, both of you need to maintain regular visits to your eye doctor. Age generally makes most everyone farsighted and other things like cataracts and macular degeneration can turn a person’s “perfect” vision into anything but.