In the context of visual acuity, what does a lower denominator indicate?

A lower denominator in the context of visual acuity signifies better vision capability. Visual acuity is commonly measured using a Snellen chart, where the top number typically represents the distance from which the test is conducted (usually 20 feet in the U.S.), and the bottom number indicates the smallest size of letters that a person can read at that distance.

Thus, if an individual has a visual acuity score of 20/20, they can see at 20 feet what an individual with normal vision can see at that distance. However, if a score were to be 20/15, the lower denominator (15) indicates that the individual can see at 20 feet what a person with standard vision could only see at 15 feet. Therefore, the person has better-than-average visual acuity. This understanding of visual acuity provides insight into a person’s eyesight and overall visual performance.