What is 20/20 Vision?

CHICAGO, IL, August 01, 2012 (Press-News.org) The term "20/20 vision" is used to indicate someone's clarity of vision (or "visual acuity") when measured at a distance of 20 feet. A person with 20/20 vision can clearly see all objects that should normally be seen at a 20-foot distance. In contrast, a person who has 20/100 vision must be 20 feet away from an object in order to see what a person with normal visual acuity can see at 100 feet. LASIK eye surgery is capable of correcting your vision to 20/20 or better. The vast majority of patients at Doctors For Visual Freedom achieve 20/15 vision after LASIK. That means what the average person needs to be 15 feet in order to see an object, a person with 20/15 can be 20 feet and still see the object.

20/20 Vision vs. Perfect Vision

Contrary to popular belief, 20/20 vision does not necessarily indicate perfect vision. It simply means your vision is sharp and defined at a certain distance. There are many other important factors that go into perfect vision, including:

- Depth perception
- Eye coordination
- Peripheral awareness (side vision)
- Focusing ability
- Color vision

All of these factors affect your overall visual acuity.

Measuring Vision with an Eye Chart

During a routine eye test, your eye doctor will use an eye chart to measure your visual acuity from a 20-foot distance. The Snellen eye chart is the most common type of chart, with eleven rows of capital letters. The top row contains one letter (usually a large "E"), while the other rows contain several letters that are progressively smaller. Your eye doctor will ask you to find the smallest line of letters you can accurately read.

Eye charts can be designed in different ways, but in most cases, if you can read the large "E" at the top of the chart but no letters below it, your vision is considered 20/200. This simply means that a person will normal vision would be able to read the same letter at 200 feet away. If your best distance vision with glasses or contact lenses is 20/200 or worse, you are considered legally blind.

In order to obtain a driver's license throughout most of the U.S., your best-corrected vision must be at least 20/40.

Better Than 20/20 Vision?

Although 20/20 vision is considered "normal visual acuity," it is not the best visual acuity there is. For example, the last three lines of letters on a Snellen eye chart indicate 20/15 vision and20/10 vision. The best vision that a person can theoretically have is 20/7.5. Very, very few people have 20/10 or better natural vision, but several types of animals do, including birds of prey.

If you would like more information about visual acuity or LASIK eye surgery, please visit the website of experienced Chicago LASIK surgeon Dr. Mark Golden at Doctors For Visual Freedom at www.doctorsforvisualfreedom.com.