By Dr. Ryan W. Nelson
Quality of vision is most often measured using Snellen acuity. The Snellen system uses standard letter sizes at a fixed distance of 20 feet to quantify an individual’s ability to see. For example, if you have 20/20 vision, at 20 feet you can see what the normal eye can also see at 20 feet. Confusing? You bet it is. Here is another example. If your vision is poorer, say 20/40, then the normal eye can see at 40 feet what you can only see at 20 feet.
Some individuals are able to achieve better than 20/20 vision. A visual acuity of 20/15 means that you can stand back at 20 feet and read the same sized letter that a normal person has to move 5 feet closer to see. Impressed? Did you know that the human eye has been measured to a resolution of 20/7!
Most Snellen charts use various letters, but tumbling “E” and picture optotypes can help optometrists test the vision of young children more easily. Snellen acuity is not the only way to test vision either. In fact, there are many methods; some even measure other aspects of vision, such as contrast sensitivity.
To test your eyes, schedule an appointment at our office today.
Iowa Eye Care Eye Chart
I think I was something crazy like 20/800 before I got my LASIK surgery at Iowa EyeCare. Now, five years later, I’m at 20/15! I love it!
Thanks for the great work you do!
Good article Dr. Nelson! It was informative. Do you have a picture of the Snellen chart?
Ask and you shall receive: I’ve attached a snellen chart for your reference.
Thanks!