20/20 vision is a term eye doctors use to describe healthy eyesight. It’s a measurement of how well the average individual can read a standard chart. Here’s a closer look at how 20/20 vision is determined and whether it really means a person has "perfect" eyesight.

The 20/20 Measurement

An eye chart assesses your visual acuity, which means the sharpness of your vision. The top number in the equation is the number of feet you are standing or sitting from the eye chart when reading it.

The bottom number is the distance at which an average person is standing or sitting from the eye chart when reading the same line. The bottom number is not at all arbitrary; it helps eye doctors maintain a standard when gauging a person's eyesight, allowing them to better determine when a patient's vision may be below—or above—the average person's.

As a result, the patient can receive vision correction like glasses or contacts in the needed strength, and the eye doctor can be alerted to changes in vision that need to be monitored or explored with further testing. 

"Perfect" vs. "Normal"

20/20 eyesight is not perfect eyesight; it is simply normal. People assigned a higher number above the lower number possess above-normal vision, meaning they can see the eye chart with greater visual acuity than the average individual at the same distance. If the bottom number is higher than the top number, the person's eyesight is below normal.

20/20 means that from 20 feet away, you can read the same lines that the average person can read from the same distance. 20/30, meanwhile, means you must stand 20 feet away to read what those with normal eyesight can see at 30 feet. The goal of glasses and contact lenses is to bring vision as close to 20/20 as possible.

Bear this information in mind next time your eye doctor gives you an eye test. Midwest Eye Center: A Division of TriState Centers for Sight offers eye care services to the greater Cincinnati, OH, and northern Kentucky area. They provide eye surgeries and procedures designed to maintain your vision, including LASIK, glaucoma treatments, and corneal transplants. Call (859) 525-6215 or visit their website to schedule an appointment.