Almost half the people in the U.S. have some kind of eye defect. Nearsightedness, farsightedness, and astigmatism are most common.
If you have “20/20 vision,” what you see at 20 feet is what should be seen at that distance. It means you can see detail clearly. However, it doesn’t always mean you have “perfect” vision. For example, it doesn’t describe peripheral (side) vision and color vision.
