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What Does Having 20/20 Vision Mean?

Suppose you’ve ever had your eyes tested, or had a comprehensive eye examination with your optometrist, eye specialists, or even school vision screening. In that case, you may have heard about the term 20/20 vision. You’ve heard your friends, family, and perhaps your work colleague saying they have perfect 20/20 vision last time they had their eyes tested with their optometrist. But what does the term 20/20 really mean? Could you have vision better than 20/20?

Understanding Your Vision

We all can understand that your vision can be “clear” or “blurry.” Imagine taking a photo with your camera. If your lens is out of focus, then it produces a blurry image. If your camera is completely in focus of the subject, then the image is sharp. Many ways, our eyes function like a camera and our own natural lens inside our eyes adjusts automatically to produce a clear image of what we are seeing. But what happens when our natural lens cannot cope or adjust itself enough to produce a clear image?

Quantifying Your Vision

Think about a time when you take off your glasses, and the entire world around you is blurry. You might recall yourself doing a bit of squinting trying to read your book or watch TV without glasses. You might also remember that you naturally would start adjusting the distance you hold your book, or perhaps moving a bit closer to the TV to see a bit clearer.

The distance of where you hold your book, or how close you need to sit in front of the TV is what we, optometrists and other eye care professionals use to quantify your vision. So say, for example, you need to sit 1 metre in front of the TV, we can denote your vision as “1” if your friends can watch the TV at 3 metres, the vision of your friends could be denoted as “3.” If we were to draw a comparison of your vision between your friend and yourself, we write it down as “1/3” meaning, your friends can see 3x as better than you, or, your vision is only 1/3 of what your friend is.

Using the ” 20/20″ Notation

With the example above, we can compare your vision with your friend. But what if your friend has poor vision? So, there is a need to standardise how and perhaps, whose vision is compared to.

The eye care community decided to compare and measure the vision of their patients with “Bob.” Bob has perfect vision. The scientists have come up with ways of understanding Bob’s vision by running through countless tests on the human retina and working out our eyes’ resolution. Bob is deemed to have perfect vision through these numerous tests, or vision we optometrists expect our patients to have.

Using the same TV example, we asked Bob to step away from the TV until he can no longer recognise the subtitles. We measure this distance, and it happens to be 20 feet. From there, the eye care community have decided at 20 feet, a patient with normal vision should be able to read the subtitles on the television.

The scientists measure this particular letter’s size and then scale it to measure the patient’s vision in a standard consultation room. Instead of using one letter of a specific size to measure vision, we can use different sizes to emulate the distance of where Bob needs to be to recognise it. For example, a bigger letter means, Bob can be a little further away to see it. A smaller letter means Bob needs to be a bit closer to recognise it.

Since we have used 20-feet as a standard, the way we quantify vision is compared to this. So for someone having 20/20 vision, means they have the same vision as Bob. Someone having 20/40 vision, means Bob can see what you see at 40 feet, whereas you can only see it at 20 feet.

But in Australia, We Use the Metric System!

That’s right; we don’t use feet as a common unit of measure. But we can easily convert 20 feet to metres which works out around about 6 metres. So instead of 20/20 vision, we call it 6/6 vision.

Could You Have Better than 20/20 Vision?

The short answer is yes, you can! The term 20/20 only describes what we expect our patients to see when they come into our consultation rooms. And plus, that’s Bob’s vision anyway. Everyone’s vision is different. Some could be better or worse than Bob’s vision. Just like someone who can hold their breath underwater longer than others.

The Bottom Line

Having vision less than 20/20 doesn’t always mean you have poor eyesight or start developing some eye disease. It is only concerning if your vision has changed dramatically over time.

The only way to measure any subtle changes to your vision accurately is to ensure your vision is checked under the same conditions as your previous eye tests. This means, your vision is checked by the same clinic, with the same optometrist.

Your vision may fluctuate from day-to-day. For example, your vision might not be at your best when you’re tired. During the examination, our eye examination uses the best technology available to ensure no subtle changes at the front and back of your eyes, that could be contributing to any vision changes. This includes an OCT scan, which produces a cross-sectional image of your retina in high definition, as well as a corneal topographer, which measures any subtle changes at the front of the eye such as any significant astigmatism.

To see if you have 20/20 vision (or better), schedule an appointment with us online. We look forward to getting to know you at our modern optometry practice.