What does 20/20 vision mean?

Submitted by Josh Talkington on September 13, 2011

The most common way to measure visual acuity is with an eye chart of a certain size, viewed from 20 feet away. Most Ophthalmologists offices are not 20 feet long anymore, but will use mirrors to simulate a 20 foot distance.

The numbers 20/20 is a comparison of your vision to perfect or normal vision. Therefore, if what you can see at 20 feet away is the same as a person with perfect vision, you are considered 20/20. If what you can see at 20 feet away, a person with perfect vision can see at 40 feet away, your vision is 20/40, and so on. While 20/20 vision is considered “perfect” vision, it is possible to see better than 20/20.

While this convention works well for measuring distance vision, it does not work for measuring the ability to read at close range. Most Ophthalmologists use a scale called the Jaeger scale, which again is based on specific sized letters, held at approximately 16 to 18 inches away.

LASIK, glasses and contact lenses are all designed to improve your visual acuity, be it for distance or for near.