What Does 20/20 Vision Mean?

The saying “hindsight is 20/20” implies that you can look back and see things more clearly, usually meaning you have an advantage to how you can see things better. The term “20/20 vision” is similarly referred to as the standard or optimal number in vision clarity. It is common for patients to think that seeing 20/20 is the highest quality vision and the ultimate perfect score when reading an eye chart. But what does 20/20 vision mean and is it an accurate indication of how well one can see?

Ever since childhood when you would be asked to read one line at a time of an eye chart at the school nurse’s office, you have heard about “20/20 vision”. The 20/20 number measures visual acuity, meaning the clarity or sharpness of vision. Up until the mid-1800’s, corrective eye care was fairly one size fits all without the ability to create custom prescriptions based on visual acuity measurement. In 1862, a Dutch ophthalmologist named Herman Snellen created the famous eye chart with the large E at the top still used by eye doctors today. Each line on the Snellen chart is 25% smaller than the one above it. Having 20/20 vision means that one can see the same amount of detail at 20 feet away as the average person who does not require corrective lenses. 20/20 vision means that one can see an object clearly, crisply, and without blurriness at 20 feet away. In other parts of the world 20/20 vision is referred to as 6/6 vision for countries who measure in 6 meters versus 20 feet. As 20/20 is two 2 parts, the first 20 refers to the distance at which the test is conducted and the second 20 is the distance at which the smallest standardized letters on the Snellen chart known as optotypes should be clearly visible. When a patient is unable to read a line of letters without strain or squinting, this is where the doctor can determine visual acuity and prescribe corrective options to improve vision. The further down on the chart you can see, the closer your sight is to 20/20 vision. The eighth row of the chart is 20/20 visual acuity. 

Keep in mind that visual acuity is just one component of a comprehensive eye exam to evaluate vision. Other vision abilities will still need to be tested including peripheral awareness, eye coordination, depth perception, focusing ability, and color vision. For your eye exam call Skyline Vision Clinic at 719-630-3937 or visit online at WEBSITE.