mrta
mrta login
missouri teacher retirement
retired teachers
Missouri teachers
teachers retirement association
www mrta us
retired teachers association
mo teacher retirement
missouri state teachers association
missouri public school retirement
missouri state teachers retirement
missouri retired teachers association
retirement in missouri
www.mrta.us
teacher retirement missouri
teacher retirement association
mrta com
missouri retired teachers
missouri teachers retirement
mrta.us
retired teacher association
mrta org
missouri teachers pension
retired school teachers
www mrta com
missouri teachers
www mrta
missouri teachers union
missouri education association Image

The Origins of the Eye Chart

May 1, 2021

Here’s a great trivia question: Who is the individual responsible for the best-selling poster of all time? Edward Hopper for his “Nighthawks” diner scene? Farah Fawcett for her 12-million selling 1970’s swimsuit poster? Or even that painting of dogs playing poker by Cassius Marcellus Coolidge? These would all be good guesses. But the correct answer is Herman Snellen.

Who??? You might be unfamiliar with the name, but you definitely know his work. More copies of that poster have been printed and sold in America than any other. You’ll find it - and its electronic descendants - in the offices of optometrists, ophthalmologists, school infirmaries, and, especially, Department of Motor Vehicles locations.

The poster is, of course, the famous eye chart that is the standard tool for eye doctors to check “central visual acuity”, or the sharpness of the vision that's directly in the center of the retina.

The idea for the chart came from Dr. Herman Snellen (1831-1908). Snellen was a professor of ophthalmology at the University of Utrecht, in the Netherlands. In the 1860s, he determined what the world needed was a standardized method to test vision based on letter recognition. Snellen chose letters because in order to distinguish one letter from another the eye must be able to distinguish the spaces between the lines which correspond to a visual angle of pi. In other words, can you tell an R from an O? An N from an M? What's important is the size and contrast of the letters, not what the individual letters are.

How profound of an impact did the chart have on measuring vision? Consider this: the Snellen eye chart isn’t pegged to 20/20 sight, it's the other way around. Snellen’s eye chart is the yardstick that established 20/20. If, from a distance of 20 feet, you can read a line that "normal" sight would enable you to read at 20 feet, your sight is termed 20/20. For instance, the top line of the chart usually has just one letter (usually a big “E”). That’s set at 20/400. If that's all you can make out on the chart, that's what your vision is considered. Most charts smallest lines are either 20/15 or even 20/10.

These days, there are several options that allow you to casually test your sight based on the Snellen eye chart, including online tests. But even if you score an impressive 20/10 in an online quiz, regular check-ups with your eye doctor are still essential. Not only is the Snellen eye chart unable to measure peripheral vision, depth perception, color perception or ability to perceive contrast, only your eye doctor can measure items related to the health of your eyes, such as whether you may have glaucoma, your eye fluid pressure, how dry your eyes are or if your retinas are in good shape. 

Eye chart testing is just one component of a complete eye exam. While knowing the name “Herman Snellen” is great for trivia games, a Vision Plan from MRTA and AMBA is an even better idea to help you save on check-ups, prescriptive lenses, and more. Learn more here or call 866-979-0497.

Source: https://www.allaboutvision.com/eye-test/free-eye-chart/

Share:
RECENT POSTS
Is Using Your Phone A Pain the Neck?
Is Using Your Phone A Pain the Neck?

Bad Posture While Using Your Device Can Injure Your Neck Do you have tension in your neck, shoulders, or even in your upper


Read More

Helping Your Hands: Preventing and Treating Carpal Tunnel Syndrome
Helping Your Hands: Preventing and Treating Carpal Tunnel Syndrome

Ever notice your hands feel weak and tingly after a day typing away at the keyboard? This could be a symptom of carpal tunnel


Read More

See Elvis’s America with AMBA Passport
See Elvis’s America with AMBA Passport

With Baz Luhrman’s new smash hit film “Elvis” reigniting passion for the King of Rock and Roll, there


Read More

 Burger Night with a Healthy, Delicious Twist: How to Make Salmon-Spinach Burgers
Burger Night with a Healthy, Delicious Twist: How to Make Salmon-Spinach Burgers

When you think beyond the usual combos, a whole new world of juicy flavor awaits. With this recipe from one of our readers, we


Read More

©2020 Missouri Retired Teachers Association. All Rights Reserved.