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What is perfect eyesight?-What does it mean when you are told to have 20/20 vision?
With good eyesight, you can go anywhere freely and lead an independent life. You may be having a 20/20 vision, but do you know that having 20/20 vision does not mean you have perfect eyesight?
It simply means that you can see objects clearly from 20 feet away, as clearly as a person with normal-sighted can see from a distance of 20 feet away. The metric equivalent is 6/6 vision where the yardstick is 6 meters. Both are measurement of your visual acuity. In other words, it gauges how sharply or clearly you can see something from a distance.
In the term ‘20/20 vision’, the numerator refers to the distance in feet between where you are standing and the eye chart, usually the classic Snellan chart. On the other hand, the denominator refers to the distance from where a person with typically normal eyesight can see clearly. The numerator is a constant while the denominator gives an indication of your visual acuity.
If you are nearsighted and have a vision of 20/60 vision, it means that objects beyond 20 feet are fuzzy to you. They are so fuzzy that what you can see from 20 feet away is what people with normal vision usually can see from 60 feet away. By the same token, 20/150 vision means that what you can see from 20 feet away is what people with normal vision can see from 150 feet away. The bigger the denominator, the weaker is your visual acuity or poorer your eyesight.
When you are told to have 20/20 vision, your vision is considered “normal” as most people can see what you can see from 20 feet away. However, some people can have vision even better than 20/20, like 20/10. This means that while they are 20 feet away from a target, they can see so well that they can see what a normal person can see from 10 feet away. They are said to have more acute vision than most people and they probably do not need binoculars as much as most other people.
With a vision of 20/20, you are right to be happy to be able to lead a normal life. There is however no such thing as perfect vision because there are many other factors besides the visual acuity which can affect your ability to see well. During an eye examination, a doctor will not stop after establishing you have 20/20 vision.
In a routine eye examination, you will be examined for your depth perception, colour vision, peripheral vision and ability to focus on close objects. It is advisable to go for routine eye examination even when you have 20/20 vision.
Anyone here have better than 20/20 vision? Tell us about it.
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