We've all stumbled upon the expressions 20/20 vision and visual acuity. As common as these terms are, do people really know what they mean?
20/20 refers to the sharpness of eyesight measured at a distance of 20 feet. If you have 20/20 vision, that basically means that from a distance of 20 feet you are able to accurately see that which should be seen from that distance. And did you know that 20/20 is just a standard measurement? The truth is, a lot of people have vision that's better than 20/20; for example, some people have 20/15 vision, so what they could see at 20 feet, a person with normal vision might only be able to discriminate at 15 feet.
Your eyes are examined separately. When your optometrist asks you to read the letters on the eye chart, the smallest row that you can read properly determines the visual acuity in the eye being examined.
It's important to recognize that 20/20 vision actually doesn't mean you have perfect vision, because it can only judge your distance vision. There are lots of equally important components to seeing properly; being able to focus on close objects, contrast sensitivity, peripheral vision, eye coordination, depth perception and color vision - these are all extremely important to your overall vision. Furthermore, a person who has 20/20 vision can have plenty of other eye-related health problems. Even those who have suffered damage to the retina due to glaucoma, diabetes, high blood pressure, or numerous other conditions might still have 20/20 vision without glasses. For this reason, an eye care professional will always carry out a comprehensive eye exam, and not just a plain visual acuity test.
During your next eye exam, you'll know what we're looking for when we ask you to read from an eye chart!