Generally, the goal of correcting vision with glasses or contacts is to bring a person’s vision to 20/20, but what does that really mean?
An eye chart measures the clarity or sharpness of vision. The top number refers to your distance in feet from the chart. The bottom number indicates the distance at which a person with normal eyesight can read the same line.
20/20 vision is considered to be “normal” vision. A person with 20/20 vision sees the same line of letters on an eye chart from 20 feet away that a person with normal vision sees at 20 feet.
If you have 20/30 vision, it means your vision is below 20/20. When you are standing 20 feet from the chart, you can read letters that most people see when they are 30 feet away.
A person can have 20/15 vision, which is sharper than 20/20. If you have 20/15 vision, you can see a line in the eye chart at 20 feet that the average person can only see when they are 15 feet away.
Only about 35% of all adults have 20/20 vision without glasses, contact lenses or corrective surgery. With corrective measures, approximately 75 percent of adults have 20/20 vision. In almost every state, visual acuity of 20/40 or better is required for an unrestricted driver’s license. People are considered “legally blind” if their corrected vision (with eyeglasses or contacts) is 20/200 or worse.
Visual acuity as measured by an eye chart is only one part of an eye exam. Other tests performed during an exam by an Ophthalmologist can detect early signs of eye diseases that can result in vision loss if untreated.