WHAT DOES 20/20 MEAN? By Dr. James Ivanoski, Optometrist at Lakeshore Eye Care Professionals with offices in Mequon & Saukville, Wisconsin
The minimum separation the average person can see between two lines is 1 second of arc or 1/60 of a degree. Using a mathematical formula, it can be calculated that this translates to a letter size of 8.75 mm or 0.35 inches high is what the average person should be able to see 20 feet away. So a person that can see 20/20 can see as small as a 0.35 inch letter at 20 feet. A person that sees 20/100 can only distinguish a 1.75 inch or larger letter 20 feet away. In other words, what a 20/20 seeing individual can see at 100 feet, a 20/100 seeing individual would have to be 20 feet away (5 times closer) to see the same thing.
The visual acuity charts that we use are all based on these letter sizing calculations. Herman Snellen was the ophthalmologist that invented the first standardized eye chart in 1862. We still use similar charts to measure vision today. Our vision charts are projected or digital, and we use a mirror to simulate a 20 foot long room. At Lakeshore Eye Professionals our passion is to try to keep everybody seeing as close to 20/20 as possible for their entire life, especially now that you know what it means!
Dr. James Ivanoski is an Optometrist practicing at Lakeshore Eye Care Professionals with Dr. Martha Jay and Dr. Mark German. He welcomes patients of all ages into his practice and accepts most insurance plans. For more eye care information, call 262-241-1919 or visit www.LakeShoreVision.com