Though 20/20 is widely considered to be “good vision,” some people can actually see better than 20/20. Different eyes can measure differently for example, it’s possible to have an eye that sees 20/20 and another that sees 20/40. Importantly, this ratio is not a measurement of overall vision quality. In other words, the letters will appear blurry and difficult to read. Someone with 20/40 vision will stand 20 feet away from an eye chart, and see the letters as if they were 40 feet away. People with 20/20 vision will be able to see the letters on an eye chart clearly from 20 feet away. The second number can change, and it stands for the perceived distance. The first number stands for the distance between the patient and the Snellen eye chart (it’s always 20 feet). To measure acuity, doctors have their patients sit or stand in place and read a stationary poster, known as the Snellen eye chart.Ģ0/20 is a ratio of distances calculated in feet. Visual acuity, or how well you see objects while standing still, is made up of three factors: how the brain communicates with the eyes how the retina and the brain’s vision center cooperate and how the cornea and lens interact to focus light onto the retina. If you wear glasses or contacts, you probably know that your optometrist is trying to correct your vision to “20/20.” Sure, having 20/20 vision means you can see well, but what do those numbers actually mean – and how are they calculated? Find out what it means to have 20/20 vision, and whether or not it really is “perfect.” Calculating 20/20 Here’s what it actually means to have 20/20 vision, and why it’s just one part of assessing the quality of your eyesight.
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