Visual acuity (VA) is acuteness or clearness of vision, especially form vision, which depends on the sharpness of the retinal focus within the eye, the sensitivity of the nervous elements, and the interpretative faculty of the brain.
VA is a quantitative measure of the ability to identify black symbols on a white background at a standardized distance when the size of the symbols is varied. The VA represents the smallest size that can be reliably identified. VA is the most common clinical measurement of visual function.
Some people may suffer from other visual problems, such as color blindness, reduced contrast, or inability to track fast-moving objects and still have normal visual acuity. Thus, normal visual acuity does not mean normal vision. The reason visual acuity is very widely used is that it is a test that corresponds very well with the normal daily activities a person can handle, and evaluate their impairment to do them.
- 20/20 Eyesight is Not Necessarily Perfect Archived 2007-05-27 at the Wayback Machine Catalog of Stories by Parents of Children Who Tested 20/20, Optometrists Network
- Visual acuity measurement Archived 2007-04-02 at the Wayback Machine The Ophthalmology Teaching Website, Faculty of Medicine, University of Toronto
- Visual Acuity of the Human Eye Archived 2012-09-06 at the Wayback Machine
- Golovin-Sivtsev Table for testing visual acuity - used in the USSR and post-Soviet states
- Visual Acuity Archived 2009-03-01 at the Wayback Machine Chapter from the Webvision reference, University of Utah
- Blur simulator (for eyeglass prescriptions)