Are you aware that 20/20 eyesight measures only one component of our vision? Though we often think 20/20 vision is perfect, is it really?
Most of us grew up equating 20/20 vision with perfect vision and at a certain point, it seemed that having “the best” eyesight was a goal for which we needed to strive. However, many years of education and learning later have taught us that there is no such goal. Perfect vision, it seems, is a myth. And the biggest surprise of all is that 20/20 vision is merely average. In fact many competitive athletic programs screen their athletes to assess much more than 20/20 vision including visual skills such as spatial awareness, depth perception, hand-eye coordination, color contrast, and peripheral vision.
When we talk about 20/20 vision, it’s important to know what the numbers mean and how they've come to define how well, or not, we see. In the United States, where distance is measured in inches and feet, the number 20 represents the number of feet between patients and the standard E chart optometrists use to test visual acuity. In turn, your ability to see clearly is based on how well you can read the letters and numbers on the chart from this distance. In the UK and other countries that use the metric system, 20/20 vision is known as 6/6 vision, an indication of how many meters rather than feet, stand between patient and chart.
The Snellen 20/20 fraction, named for the ophthalmologist who created this system, corresponds to two distinct factors. The top number of the fraction represents the distance between the patient and the chart, and the bottom number corresponds to lines on the chart. If for example, you can read the large E at the top from a distance of 20 feet, you have 20/200 vision. Because the system measures how well people see on average, 20/200 actually indicates rather poor visual acuity. To further clarify, 20/20 vision is a measure of how well the average person sees, not the one with unrealistically “perfect” vision.”
If you have been told you have 20/20 vision, chances are you don’t need glasses, contact lenses, or magnifiers to see or read clearly. If however it is determined that you are nearsighted (meaning, you see well when things are close up), farsighted (you’re able to see things in the distance clearly), or a combination of the two, you’re likely to need corrective lenses. Regardless of whether or not you need glasses, it is important to remember that the sum total of your vision cannot be based on how well you read the E chart.
If 20/20 isn’t a true measure of how well your eyes work, how do you know when you have a vision problem?
Vision tests administered in schools are not the be-all, end-all to vision screening, but they can give you a good starting point to identify if your child sees and if they need help. It’s important to understand that these screenings cannot detect a number of visual deficits, which is why reliance on them as proof of “perfect vision” is highly discouraged. According to the College of Optometrists in Vision Development, the most common vision problems are not associated with visual acuity (20/20 vision).
Still, the results of any school vision test should be brought to your eye doctor, as they can compare what they see in-office to what’s been recorded in school.
If you’re experiencing blurred vision, headaches, neck strain, dizziness, have difficulty with recall, reading comprehension, or other significant visual functions, it is important you see our eye doctor for a functional vision exam. Although you or your child may not need corrective lenses, you may be a candidate for vision therapy. It is important not to place too much trust in a school screening that only assesses 4% of a functional vision examination; this screening will not reveal many vision problems.
It is important and, frankly, good practice to have your eyes, as well as that of your family members, checked at least annually. 20/20 vision isn’t about having “perfect” vision and doesn’t give you a full picture as to what your eyes can really do. Remember too, that if you or your child struggle with any key visual skills, it's best to contact our optometrist. It’s possible you’ll need glasses or perhaps vision therapy. Our eye doctor is the one who can guide you best and recommend the interventions that are right for you.