20/20 vision means that vision is normal at a distance of 20 feet. If a person can only see at a distance of 20 feet what the average person can see at 40 feet, he has 20/40 vision. If a person can see at 20 feet what the normal person can see at a distance of 15 feet, he has 20/15 vision or better-than-average vision. While these figures measure the ability to see straight ahead, it is also necessary to have good peripheral (side) vision, eye coordination, depth perception, color vision and night vision.