5/4/2023 0 Comments 2020 visionThe Snellen test uses a printed chart that has rows of letters that decrease in size from top to bottom. Snellen charts, or the Snellen system of visual acuity, are the most common tools for testing vision in the United States.It also does not automatically indicate good eye health, which is why yearly dilated eye exams are important, even if someone is told they have 20/20 vision. It does not take into account important things like color vision, depth perception, contrast sensitivity, peripheral vision, or how a person’s eyes work together. It is also measured in a stationary setting and under high contrast conditions. 20/20 vision does not always mean “perfect vision.” 20/20 only refers to a person’s visual acuity and what he or she can clearly discern at a distance. This phenomenon results in the majority of the population needing glasses for reading at some point, whether they are 20/20 at distance or not. In presbyopia, the lens, which was once soft and flexible, becomes rigid and unable to focus on near objects as well. This condition is called presbyopia, and it is a normal part of the aging process. Another common misunderstanding is when people with 20/20 vision who have previously not needed glasses start developing blurry vision at near around the age of 40. if someone’s visual field is 20 degrees or less, he or she is considered legally blind. One’s peripheral vision is also considered. Patients frequently say that they are, “legally blind without their glasses.” By definition, someone is legally blind if his or her better eye is 20/200 or worse without corrective lenses. If a person does not have 20/20 vision, it could be due to a variety of reasons, such as nearsightedness, farsightedness, astigmatism, or an eye disease. 20/15 indicates that one is able to see at 20 feet what someone with normal vision can see at 15 feet. It is, in fact, possible to see better than 20/20. So, if someone has 20/40 vision, they can see at 20 feet what someone with normal vision can see at 40 feet, and if someone has 20/100 vision, they can see at 20 feet what someone with normal vision can see at 100 feet. The top number is the distance from the chart (in the United States, this is 20ft), and the bottom number is the distance from which someone with “normal” eyesight can read the same line. ![]() ![]() If a patient is unable to read, a system of numbers, symbols, or a “tumbling E” are sometimes used. The rooms are actually much shorter than that. These are normally used in an “optically folded” exam room, meaning that mirrors are used to help create an optically 20-foot-long room. ![]() The most common method of measuring a person’s visual acuity is the Snellen chart, which consists of uppercase letters that get increasingly smaller line by line. So if a person has 20/20 vision (or “normal vision”), they can see clearly at 20 feet what should normally be able to be seen at 20 feet. During a visual acuity test, that standard distance is 20 feet. The term “20/20 vision” refers to a person’s visual acuity, or in other words, their ability to read numbers or letters on an eye chart at a standard distance. As eye care providers, we often get asked, “What does 20/20 vision actually mean?” You might be surprised to find out the term comes from measuring the sharpness of your vision.
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