![]() The measurement of 20/20 vision therefore represents the distance from which you can read text (20 feet) and what level of visual acuity that represents compared with the benchmark of people with normal vision. If you have 20/40 vision, it means people with normal vision can read from a distance of 40 feet what you can read from 20 feet. If so, this means that you must be as close as 20 feet to read what people with normal vision can read from 30 feet away. However, if you can’t read the 20/20 line accurately, maybe you can read the 20/30 line accurately. If you can, it means that you can accurately read the same line of block letters from a distance of 20 feet that other people with “normal” vision can read at 20 feet. So-called “normal” vision is measured by whether or not you can read the 20/20 line. ![]() However, most people can’t read down to the 20/10 level. If you can read all of the lines on a standard Snellen chart ― which tests visual acuity down to 20/10 (or 20/5) accuracy ― you have outstanding visual acuity indeed! This level of precision helps to obtain a consistent measurement of each person’s ability to identify the progressively smaller and smaller letters on the chart’s descending lines from a predetermined distance of 20 feet.Īs the patient reads the eye chart with each individual eye, your optometrist records how many letters you correctly identify on each line of the chart. The “optotype” used for the block letters on the Snellen chart is specially developed so that each letter has uniformly thick lines with uniform white space gaps between each letter, each line, and the gap in the letter “C.” The Snellen chart features eleven lines of block letters that people familiar with the alphabet should easily be able to recognize - that is, if they have the visual acuity to do so as the letters get progressively smaller as you move down the lines of the chart. Some optometrists use one of the newer eye charts, including the LogMAR, Bailey-Lovie or ETDRs chart – all of which provide a similar way to measure visual acuity. He created it more than 150 years ago in 1862 to measure how well his patients could see. The Snellen eye chart ― the one with the large “E” at the top ― is named for Dutch eye doctor Herbert Snellen. ![]() Optometrists can calculate a measure of your individual visual acuity by testing one eye at a time from a specific viewing distance using a Snellen eye chart. Visual acuity is the term used to express how sharp your vision is. Let’s examine some of the aspects around how we measure your vision when you come in for your annual exam. Having 20/20 vision is the gold standard of visual acuity or “clarity,” and it’s the level of quality in vision we aim to achieve with each patient by providing the highest possible level of comprehensive eye care and vision correction. ![]() The term 20/20 vision represents a benchmark in visual acuity that means a person has excellent vision. ![]() Which brings up an interesting question: What exactly do we mean when we say someone has 20/20 vision? Why? Because we want to help all of our patients to enjoy 20/20 vision both in the year 2020 and for many years into the future. It sounds so futuristic it’s a new decade and a year we’ve been eagerly anticipating here in your optometrist’s office. ![]()
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