It's safe to say that everyone has stumbled upon the expressions 20/20 vision and visual acuity. As frequently used as these terms may be, do people really know their meaning?
20/20 vision is used to indicate the sharpness of sight from 20 feet away. When you have 20/20 vision, that basically means that from 20 feet away you can see what should be seen from that distance. Are you aware that 20/20 isn't the best possible visual acuity? Many people can even see better than 20/20; for example, vision that measures 20/15, so what they would be able to see at 20 feet, a person with normal vision would only be able to discriminate at 15 feet.
Each of your eyes is tested separately. When you're asked to correctly read letters from the eye chart, the smallest row that you can read clearly determines the visual acuity in the eye that's being evaluated.
But 20/20 sight doesn't always mean that your eyesight is totally free of flaws, because, after all, it can only judge your distance vision. Other important vision skills; your ability to focus on objects in your immediate surroundings, contrast sensitivity, peripheral vision, depth perception, eye coordination and color vision - these are aspects of healthy vision. And actually, someone who has 20/20 vision can have eye problems. Even those who have suffered damage to the retina from diabetes, high blood pressure, glaucoma, or numerous other diseases can still have 20/20 vision without glasses. And because of this, your eye care professional always conducts a comprehensive eye exam, rather than just a regular visual acuity test.
When you're having your next eye exam, you'll understand why our eye doctors are asking you to read letters from the eye chart, and more!