What indicates the vision at 20 feet?

Vision at 20 feet typically refers to visual acuity, which is measured using a standard eye chart. The notation "20/20 vision" indicates that a person can see at 20 feet what should normally be seen at that distance. Lower numbers, like 20/40, indicate poorer vision, meaning that what a person can see at 20 feet is what someone with normal vision can see at 40 feet. Higher numbers, like 20/15, indicate better than average vision.