The 20/20 VISION
You may have had an eye exam where you were told you have 20/20 vision or you may have heard of 20/20 vision. Does 20/20 vision mean you have perfect eyesight? Is it possible to achieve even better than 20/20 vision? And what is “perfect vision” anyway?
To answer these questions, let’s take a closer look at vision-related terminology to fully understand how eye doctors measure the quality of your vision.
Visual Acuity –This basically means the sharpness of your vision and it is measured by your ability to identify letters or numbers on a standardized eye chart from a specific viewing distance.
Eyesight. – This basically means the “ability to see,” “the sense of seeing,” “vision,” “range of sight” or “view.” Often, the terms “eyesight” and “visual acuity” are used interchangeably.
Vision. This is a broader term than visual acuity or eyesight. It has to do with quality of vison . So In addition to sharpness of sight, the term “vision” usually includes a wider range of visual abilities and skills. These include contrast sensitivity, the ability to track moving objects with smooth and accurate eye movements, color vision, depth perception, focusing speed and accuracy, and more.
What is 20/20 vision?
The term “20/20” or “6/6” and similar fractions (such as 20/40, 20/60, etc.) are visual acuity measurements. They also are called Snellen fractions, named after Herman Snellen, the Dutch ophthalmologist who developed this measurement system in 1862.
In the Snellen visual acuity system, the top number of the Snellen fraction is the viewing distance between the patient and the eye chart. In the United States, this distance typically is 20 feet; in other countries, it is 6 meters. In Ngeria we use metres mostly. Hence “6/6”
At this testing distance, the size of the letters on one of the smaller lines near the bottom of the eye chart has been standardized to correspond to “normal” visual acuity ” this is the “20/20” line. If you can identify the letters on this line but none smaller, you have normal (20/20) visual acuity.
The increasingly larger letter sizes on the lines on the Snellen chart above the 20/20 line correspond to worse visual acuity measurements (20/40, 20/60, etc.); the lines with smaller letters below the 20/20 line on the chart correspond to visual acuity measurements that are even better than 20/20 vision (e.g., 20/15, 20/12, 20/10).
The single big letter at the top of most Snellen eye charts corresponds to 20/200 visual acuity. If this is the smallest letter size you can discern with your best corrective lenses in front of your eyes, you are legally blind.
On most Snellen charts, the smallest letters correspond to 20/10 visual acuity. If you have 20/10 visual acuity, your eyesight is twice as sharp as that of a person with normal (20/20) vision.
Is it possible to see better than 20/20?
Yes, it’s indeed possible to have sharper than 20/20 vision. In fact, most people with young, healthy eyes are capable of identifying at least some of the letters on the 20/15 line or even smaller letters on the Snellen chart.
What is “perfect” vision?
It’s nearly impossible to quantify what “perfect” vision is. A more interesting question is, “Perfect for what?”
For example, if you are driving on a sunny day, excellent Snellen visual acuity might be the main factor in your satisfaction with your vision. But your traveling companion, who has worse visual acuity than yours, might be happier with her vision in the same circumstances because she is wearing polarized sunglasses with anti-reflective coating that enhance contrast and block glare.
Or an athlete who has better than 20/20 vision might struggle with his performance because he doesn’t have certain dynamic visual skills that allow him to react to moving objects as quickly as a teammate whose static visual acuity isn’t as sharp as his.
Perfect Vision should include Normal Visual acuity, normal colour vision perception, Normal Depth perception, normal contrast sensitivity and binocular functions.
See your eye doctor
The first step to maximizing the clarity and comfort of your eyesight in all situations is to see a qualified optometrist or ophthalmologist for a comprehensive eye exam and vision evaluation to determine the quality of your vision.
If you want to maximize your dynamic vision skills for sports and other activities, seek an eye doctor who is a sports vision specialist and ask about sports vision training.
Finally, if your child has 20/20 vision but is struggling with eye strain and other vision problems in school, seek the advice of an eye care provider who specializes in children’s vision to have your child evaluated for possible learning-related vision problems.
Ready to have your eyes checked? Find an eye doctor near you.
Credit: All About Vision.