If you have an eye exam and are told you have 20/20 vision, does this mean you have perfect eyesight? Is it possible to achieve even better than 20/20 vision? To answer these questions, let’s take a closer look at vision-related terminology to fully understand how eye doctors measure the quality of your vision. Thanks to Amy Hellem at All About Vision we have those answers.
Visual acuity, eyesight and vision: What’s the difference?Visual acuity. This, literally, is the sharpness of your vision. Visual acuity is measured by your ability to identify letters or numbers on a standardized eye chart from a specific viewing distance.Visual acuity is a static measurement, meaning you are sitting still during the testing and the letters or numbers you are viewing also are stationary.Visual acuity also is tested under high contrast conditions — typically, the letters or numbers on the eye chart are black, and the background of the chart is white.Although visual acuity testing is very useful to determine the relative clarity of your eyesight in standardized conditions, it isn’t predictive of the quality of your vision in all situations. For example, it can’t predict how well you would see:
- Objects that are similar in brightness to their background
- Colored objects
- Moving objects
- How accurately the cornea andlens of the eye focus light onto the retina
- The sensitivity of the nerves in the retina and vision centers in the brain
- The ability of the brain to interpret information received from the eyes
macula) influences visual acuity measurements obtained during an eye exam.Visual acuity typically is quantified with Snellen fractions (see “What is 20/20 Vision?” below).Eyesight. The exact definition of “eyesight” is difficult to pin down. Depending on which dictionary or other resource you check, it can mean “ability to see,” “the sense of seeing,” “vision,” “range of sight” or “view.” Often, the terms “eyesight” and “visual acuity” are used interchangeably.Vision. This is a broader term than visual acuity or eyesight. In addition to sharpness of sight or simply a description of the ability to see, the term “vision” usually includes a wider range of visual abilities and skills. These include contrast sensitivity, the ability to track moving objects with smooth and accurate eye movements, color vision, depth perception, focusing speed and accuracy, and more.If this more inclusive (and accurate) definition of “vision” is used, what most people call “20/20 vision” should really be called “20/20 visual acuity.” Realistically, that probably won’t happen. For better or worse, the term “20/20 vision” is likely here to stay.