20/20 is a term commonly used as the definition of perfect eyesight. But is that really what it means? Actually, it is much more complicated than that. In fact, even the term perfect, isn’t that easily defined when it comes to your vision.
In 1862, Herman Snellen developed a system for measuring the sharpness of vision, known as visual acuity. The system measures your ability to see letters or numbers on a chart at a prescribed distance, generally 20 feet. The measurement system is known as Snellen fractions and read as: 20/20, 20/40, 20/60, etc. Using this measurement system, a person with 20/20 vision would be considered as having “normal” vision, meaning that they can see letters and numbers at 20 feet that they average person should be able to see at 20 feet. A person with 20/200 would be considered legally blind.