What 20/20 Vision in an Eye Exam Test Means

20/20 Vision: An Explanation from Family Vision Associates, Corpus Christi Texas

You've probably heard the term "20/20 vision" floated around as a kind of ideal for visual acuity. But the terminology itself will mean nothing to you if you understand how optometrists measure vision. What does it mean to have 20/20 vision -- and what should you do if your vision testing results in another number? Your friends at Family Vision Associates, Corpus Christi TX are happy to straighten out some of the confusion in this area, while providing you with the reassurance that faulty vision can be corrected.

The key to understanding the concept of 20/20 vision lies in the fact that the "20" is a measure of distance. We use standard eye charts to evaluate your ability to read text and make out individual shapes from a set distance -- and the standard for vision testing is 20 feet. That means the chart is either 20 feet away from your eyes (which would require a pretty long examining room) or it's being reflected off the opposite wall and projected at a simulated distance of 20 feet. For most patients we use the Snellen eye chart, with its characteristic giant "E" followed by 10 more lines of progressively smaller letters. For small children and certain other patients, we may project a chart showing a series of "Tumbling Es" instead. 

This kind of vision test is somewhat relative in nature, because it compares your vision against what a person with "normal" vision would be expected to see. As you read the letters at a 20-foot distance (the first "20" in a "20/20" measurement) , we check your results against what another person would be expected to see clearly from different distances. If you can see an image clearly at 20 feet that a person with "normal" vision could see clearly at 20 feet (the second "20" in the score), then congratulations -- you have 20/20 vision. If you can only see an image at 20 feet that another person could see clearly from a much longer distance (40 feet, 60 feet, etc.), then you might have a vision rating of 20/40, 20/60 or worse.

Bear in mind that 20/20 doesn't represent perfect vision -- just typical vision. 20/40 vision is generally considered good enough to obtain a driver's permit, for instance. You might even have better-than-average vision, such as 20/15.

Scheduling Eye Exams with Your Optometrist in Corpus Christi TX

Vision that falls significantly below the 20/20 mark may be the result of refractive errors, cataracts, or some other eye disorder. That's why visual acuity testing is only one part of a complete eye exam. We also examine your lens, retina and other structures to see what kind of treatment your eyes might need. We can also perform addition tests to fit you for contact lenses. Schedule an eye exam with your optometrist in Corpus Christi Texas today!