Most of us have heard the term “20/20 vision” being used in reference to healthy, normal eyesight. Perhaps you have been told you have 20/20 vision, 20/40 vision, or even 20/15 vision. As a measurement of visual acuity, 20/20 vision is considered “good” vision. Most people, however, are unaware or have forgotten exactly what these numbers mean. Let us take a quick look at the meaning behind these figures.
Anyone who has undergone a physical examination at a doctor’s office or a comprehensive eye exam at an eye clinic has seen what is called a “Snellen chart.” This is the chart hanging on the doctor’s wall with the large “E” printed at the top. This chart has been used since the late 1800’s to measure an individual’s visual acuity. Many modern eye clinics and family physicians use an electronic “viewfinder” version of the Snellen chart, but the ratios and results are the same.
Standing 20 feet from the chart, you are asked to cover one eye and read the characters on the chart. If you have 20/20 vision, then you are able to accurately read from 20 feet what someone with normal vision can read from 20 feet. Someone with 20/40 vision is able to see at 20 feet what someone with normal vision would be able to see at 40 feet, and so on.
This visual test only measures visual acuity and cannot sufficiently account for the quality of a person’s vision. Other tests are necessary to determine an individual’s ability to see color and contrast, for example. In other words, 20/20 vision is only one component of normal vision.
A comprehensive eye examination by a certified ophthalmologist or optometrist will measure both the acuity and quality of your vision, as well as help determine whether you have other eye conditions. If you live in the New Jersey area, please contact us today to arrange your comprehensive eye exam.