Everyone has run into the terms visual acuity and 20/20 vision. Yet, do people understand what these terms actually mean?
The term 20/20 indicates the clarity and sharpness of sight measured at a distance of 20 feet. When you have 20/20 vision, that basically means that from a distance of 20 feet you can clearly see what is normally seen from that distance. Alternatively, 20/100 vision indicates that to see what most people can see from 100 feet, you would have be 20 feet away.
Each eye is evaluated separately. When your optometrist asks you to correctly read letters from the eye chart, the smallest row that you can read without error indicates the visual acuity in the eye that's being examined.
However 20/20 vision actually doesn't mean that your eyesight is totally free of flaws, because, after all, it only determines your distance vision. Other vital vision skills; the ability to focus on objects that are close by, contrast sensitivity, peripheral vision, depth perception, eye coordination and color vision - these are aspects of good vision. Also, someone with 20/20 vision can still have unhealthy eyes. People with damage to the nerves inside their eyes from diabetes, high blood pressure, glaucoma, or a range of other diseases might still have 20/20 vision, without the help of glasses. And because of this, your optometrist will always carry out a comprehensive eye exam, and not just a plain visual acuity 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!