Visual acuity indicates the sharpness or your vision. It refers to the ability to recognize signs on a standardized chart from a specific viewing distance. There are several ways to express the measured visual acuity; we use the decimal as well as the 20/20-system.
Decimal: The visual acuity can be expressed in decimal or percentage for example 0.8 (80%), 1.0 (100%), or 1.2 (120%). In this system, 1.0 or 100% means the average vision, 2.0 or 200 % is the highest possible value and indicates very sharp, way above-average vision.
“20/20-vision” is widely used, especially in the US, and means that you can see clearly at 20 feet what the average person sees at that distance. If the second number is higher than 20, it means your vision is below average and if it’s smaller than 20, your vision is above average. As an example, a person with 20/40-vision sees at 20 feet, what an average person can see at 40 feet away. A person with 20/10-vision, however, can see objects clearly at 20 feet, while the average person needs to stand closer, at 10 feet, to see it.