Michael In the USA, if someone sees sharply like an eagle even without glasses, they are said to have 20/20 vision. The first "twenty" in the vision test indicates the distance of the person from the eye chart in feet. "20" therefore stands for 20 feet, which is approximately 6 meters. The second "twenty" indicates the distance from the eye chart at which a person with normal vision can still read the letters of the respective line (whose size varies). For the scientists among you, this is the distance at which the letter height corresponds exactly to one arcminute.
If someone standing 20 feet away from the eye chart sees only a blur, they might only be able to read letters that are twice as large, which a person with normal vision could recognize from 40 feet away. In that case, the visual acuity is not 20/20, but 20/40. A person with eagle eyes, who sees twice as sharply as an average person, has a visual acuity of 20/10, because they can recognize letters from 20 feet away that a person with normal vision can only decipher from a distance of 10 feet.
Unlike in Germany, where even someone who is partially blind can drive at an old age with a driver's license from their youth, Californians must take an eye test every 5 years to renew their license. At the Department of Motor Vehicles (DMV), large eye charts are displayed behind the counters. When the clerk asks you to read the letters from the third line on the second chart from the left during the license renewal process, you should be able to do so without errors. If not, you must get glasses and retake the test with them. The DMV officer will then note on your license that you are only allowed to drive with glasses.
When I took the test recently, I noticed that the letters of all the lines and all the boards follow an easily memorable pattern. It is always the same sequence, but it is rotated. So, in one line, it might say "Z F T P A G K" and in the next "P A G K Z F T". Anyone scoring over 100 on intelligence tests will surely quickly figure out the pattern. The DMV probably does this for efficiency reasons, so that the employees only have to memorize one sequence and can easily verify what is said without turning around to look at the board.