The Origin Of 20/20 Vision
Snellen is also the mind behind the concept of “20/20 vision,” or the Snellen Ratio eye doctors use to describe how well patients read the chart. Depending on how successfully you can read the lines of letters, you could have unusually good vision like 20/10 (meaning that you can see at twenty feet what most people have to be ten feet away to see), or you could need glasses to correct poor vision.
If you can’t even read the big E on top, that means your vision is 20/200 or worse. In other words, you have to be twenty feet away to see what most people can see from 200 feet.
Limitations Of The Chart
As useful as they are, Snellen’s eye chart and ratio are no longer the only factors in determining the right prescription for your glasses. Even though we still use the chart, optometry has evolved in many other ways. Your eyes might need to be tested for how well they perceive contrast, color, depth, and peripheral sight. The Snellen chart also can’t test the overall health of your eyes, like pressure, glaucoma risk, and retina shape.
How Many Lines Can You Read?
If it’s been a while since your last appointment, it might be a good time to schedule one and have another look at that eye chart—especially now that you know its history.
We’d love to see you!
The content on this blog is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.