Visual acuity

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.Cline D; Hofstetter HW; Griffin JR. Dictionary of Visual Science. 4th ed. Butterworth-Heinemann, Boston 1997. 

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.

References

 Other websites 
 20/20 Eyesight is Not Necessarily Perfect  Catalog of Stories by Parents of Children Who Tested 20/20, Optometrists Network
 Visual acuity measurement  The Ophthalmology Teaching Website, Faculty of Medicine, University of Toronto
Visual Acuity of the Human Eye 
Golovin-Sivtsev Table for testing visual acuity  - used in the USSR and post-Soviet states
Visual Acuity  Chapter from the Webvision reference, University of Utah
Blur simulator (for eyeglass prescriptions)

Category:Optometry