Who Is Dr. Snellen?
The first eyeglasses were invented between 1268 and 1300; they consisted of two magnifying glasses connected with a small hinge and balanced on the bridge of the nose. For the next several centuries, “technology” didn’t really advance much.
If you had trouble reading or seeing up close, for example, you could get glasses with convex (i.e. surface curves outward) lenses. If you had difficulty seeing into the distance, your lenses would be concave (i.e. surface curves inward). And if you had fuzzy vision at any distance, why, you’d get a pair of bifocals. As you might guess, this meant that there was half a convex lens at the bottom and half a concave lens at the top! Beyond this, glasses were very much one-size-fits-all.
This is where Dr. Herman Snellen comes into the story: he was a Dutch doctor who created the Snellen Chart. That’s the famous “E” chart we all know from our visits to the optometrist. The chart gave professionals a way to assess the visual acuity of their patients, and it’s still in use today.
A Clear Look at 20/20 Vision
As you’ll recall from your eye exams, each line on the chart is smaller than the one above it. It indicates what someone with normal vision is able to see at a certain distance. So, if you have 20/20 vision, you are able to see the same amount of detail at 20 feet as someone who does not need corrective lenses.
But what if you have 20/40 vision? Compared to the average person who does not need corrective lenses, you have to be twice as close to see clearly. Now, some people have better than 20/20 vision. For example, if you have 20/10 vision, you can see at 20 feet what an average person sees at 10 feet.
The Snellen Chart and 20/20 vision is essentially a comparison of your visual acuity against what the average person sees at the same distance.
I Have 20/20 Vision: Does This Mean I Don’t Need A Corrective Prescription?
It is not that simple. Average or above-average visual acuity does not mean that you are free and clear of other eye problems. While Dr. Snellen made a great contribution to eye health, today, we are also able to test how well you perceive color, and contrast, depth. We can see how acute your peripheral vision is, how well your eyes work together, and whether there are symptoms of health conditions, such as glaucoma, diabetes, high blood pressure, and more.
So, even if your visual acuity is on point, it does not mean you can skip your regular eye exams. There is so much more information we can gather to ensure you not only see as clearly as possible but that your eyes are as healthy as possible. Please contact Asheville Vision Associates and schedule an appointment today!