July 06, 2021
If anyone you know has it, they brag about it…endlessly! You’ve no doubt heard it many times before… “My eyesight is perfect - I have 20/20 vision!”
But is this really true? Does everyone with 20/20 vision have perfect eyesight? And if 20/20 vision isn’t perfect, what does it really mean?
While the technical definition of 20/20 vision is full of highly scientific terms and concepts such as minutes of Arc, subtended angles, and optotype size, we won’t dig down that deep. Here we’re going to break it down into a more comprehensible explanation that illustrates why a person can have 20/20 vision and not perfect eyesight.
The most important thing to remember is that only one aspect of vision is measured using this common scale. Visual acuity, or VA, is how clear or sharp your vision is. Your visual acuity may be high, but there are many other reasons why your vision won’t be perfect. Other important elements such as peripheral (side) vision, eye coordination, depth perception, focusing ability and the ability to correctly process color are all part of your ability to see correctly.
The measurement of visual acuity is what most people hear about, so to the average person, a VA measurement of 20/20 means your eyesight is theoretically “perfect”. The funny thing is…this standard itself is rather random. The basis for the 20/20 scale is as simple as this - 20/20 vision is normal VA (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at this distance. If it had been determined that the scale should reflect how clearly a person could see at the distance of 40 feet as the measurement, so-called perfect vision would be 40/40 vision!
Many people don’t have vision in this proportion, so while this scale can indicate where your visual acuity falls, it won’t determine if your vision is perfect. If you have 20/100 vision, you must be as close as 20 feet to see what a person with normal vision can see at 100 feet, meaning your VA isn’t as high as it is for most people. On the opposite end, someone with 20/15 vision will see just as clearly and sharply as a person with 20/20 vision will see at the distance of only 15 feet. Many factors can contribute to a loss of visual acuity. Nearsightedness, farsightedness, astigmatism or eye diseases will affect the clarity of vision.
The most common test of visual acuity is one you’ll immediately recognize, even if you don’t know its proper name. Behold – the Snellen Chart!
Developed in 1862 by Herman Snellen, a Dutch ophthalmologist, this chart is universally used to measure visual acuity during a vision test. Typically, the patient will be seated 20 feet away from it. The ‘E’ on the top line represents 20/200 vision. If the large E is the only thing you can read, you are considered legally blind and see from 20 feet what a person with normal VA can read from 200 feet. 20/80 vision means that you can read news headlines with ease, while 20/200 vision (legally blind) means that you can’t see anything smaller than letters on a STOP sign.
Visual acuity improves as you go further down the chart. In order to get a driver’s license, your vison must be corrected to the point where you are able to read the fifth line, representing 20/40 vision. The bottom line on the chart represents 20/10 visual acuity, and there are people who can decipher it, but it’s very uncommon. Less than 1% of the general population have 20/10 vision, however most people with young, healthy eyes can usually make out some of the letters at the 20/15 level.
So – do you know where you stand on the scale of visual acuity? It may be time for you to visit your eye doctor for a comprehensive vision exam to find the answer. If you need help reaching the vision requirements for leading the type of life you want to lead, your optometrist can provide the appropriate guidance to help you choose the perfect pair of glasses or contact lenses. At Pro-Optix Eye Care, the home of the top Houston eye doctors, we have an amazing selection of classic and designer frames, a full line of lenses in every type of material and strength imaginable and contact lenses to fit highly challenging prescriptions. Call 713-360-7095 today to schedule your personalized consultation!
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