You have most likely run into the terms visual acuity and twenty-twenty vision. Yet, do people know what these terms actually mean? Understanding them will help you appreciate how an eye specialist evaluates your vision during an eye exam.
20/20 is used to indicate the accuracy of vision from 20 feet away. If you have 20/20 vision, that means that from a distance of 20 feet you can clearly see what normal-sighted people can see from that distance. So, 20/100 vision indicates that you would need to be as close as 20 feet away to see what a normal-sighted person can see from 100 feet away. Obviously, in this scenario, it would mean that you would be pretty near sighted.
Each eye is evaluated on its own. When the optometrist asks you to read the letters on the eye chart aloud, the smallest row that you are able to read properly determines the visual acuity of the eye being evaluated.
It's important to recognize that 20/20 eyesight actually doesn't mean that your eyesight is flawless, because, after all, it can only judge how accurately you see at a distance. There are several other important vision skills; being able to focus on close objects, contrast sensitivity, peripheral awareness, eye coordination, depth perception and color vision - these are all really important to your overall vision. Furthermore, a patient with 20/20 vision can certainly have plenty of other eye-related health problems. Those with damage to the retina as a result of diabetes, high blood pressure, glaucoma, or a range of other conditions can still have 20/20 vision, without the help of glasses. For this reason, your eye care professional always performs a comprehensive eye exam, and not just a plain eye chart test.
When you're having your next eye exam, you'll know exactly why we're asking you to read letters from the eye chart, and more!