During an eye exam, you’ll be asked to read letters and numbers on a chart at varying distances. The results of this visual acuity test are interpreted by an optometrist to determine where a person falls in the normal range of vision. The measurement 20/20 is used as the benchmark to make this determination. Here is an overview of what you need to know about 20/20 vision so you can prepare to ask the eye doctor questions about your ocular health and eyewear prescription.

What Patients Should Know About 20/20 Vision

How Is It Measured?

During an eye exam, the Snellen chart and system are used to measure central visual acuity—or how the eye focuses directly on objects. With the fraction 20/20, the top number refers to a standard viewing distance of 20 feet. With normal vision, it’s possible to view objects 20 feet away or farther without straining the eye muscles used to focus.

The bottom 20 in the fraction indicates the number of feet someone with normal vision can see a particular line on an eye chart. Those with 20/40 eyesight can identify details in numbers on a specific line of an eye chart at 20 feet, while others with normal vision can see the same line clearly and sharply from 40 feet away.

What Does 20/20 Vision Indicate?

Perfect eyesight and 20/20 vision are not the same. This fraction only indicates that someone has average vision. When the bottom number is greater than 20, a person has below-average vision. Eyesight is above average when the bottom number is less than 20. Perfect vision is actually closer to 20/10.

People read the Stellen chart—named after Dutch ophthalmologist Herman Snellen—using one eye at a time without the aid of glasses or contact lenses. After reviewing the results of the test, an optometrist will have the patient read the chart again while looking through different lenses in a phoropter. This device tests individual lenses on each eye during an exam. Your glasses or contact lens prescription will be based on the lens combination that brings your vision closet to the 20/20 benchmark.

If you need to have your eyes examined to determine your visual acuity, contact Dr. Michael R. Schmit in Cincinnati, OH. This trusted optometrist works with patients throughout the Green Township and White Oak areas and has been providing eye exams to detect vision changes and diagnose ocular conditions since 1980. Call (513) 741-8811 to schedule an appointment. Find out more information and download patient forms online.