Normal vision is called 20-20 vision. these numbers are actually a ratio—a comparison of the distance you can see to the distance a normal-sighted person can see. for example, a person with 20-30 vision can see from a distance of 20 feet what a person with 20-20 vision can see from a distance of 30 feet. based on this knowledge, explain what the following numbers mean regarding vision. a. 20-100 b. 20-40