We've all heard the terms visual acuity and 20/20 vision. Yet, do people know what these terms really mean? Understanding them will help you appreciate how your optometrist assesses your vision during an eye exam.
20/20 vision indicates the clarity and sharpness of your vision from 20 feet away. When you have 20/20 vision, that means that from a distance of twenty feet you can clearly see that which normal-sighted people can see from that distance. Alternatively, 20/100 eyesight would indicate that to see what most people can see from 100 feet, you would have be 20 feet away. Obviously, if this was the situation, it would mean that you would be pretty near sighted.
Both eyes are tested one after another. When you're asked to read the letters on the eye chart aloud, the smallest letters you can properly read determine the visual acuity in the eye being evaluated.
But 20/20 sight doesn't always mean that your eyesight is perfect, because, after all, it can only judge how clearly you see at a distance. There are lots of equally crucial sight skills; your ability to focus on objects in your immediate surroundings, contrast sensitivity, peripheral vision, eye coordination, depth perception and color vision – these are all very important to your general eyesight. And actually, a patient with 20/20 vision can certainly have plenty of other eye-related health problems. Even those who have suffered damage to the sensory nerves inside their eyes due to diabetes, high blood pressure, glaucoma, or other diseases are still able to have 20/20 vision without glasses. And because of this, an eye care professional will always carry out a comprehensive eye exam, as opposed to just a simple eye chart exam.
During your next eye exam, you'll understand why you need to read letters off an eye chart, and more!