Definition of Blindness

"Blindness" is defined as visual acuity worse than 3/60 meters (10/200 or 20/400 in US terms), or a visual field of less than 10 degrees in the better eye with best possible correction. (Please Note: Since most parts of the world use the metric system, the World Health Organization uses meters in its definitions.)

Definition of Low Vision

Low vision (previously referred to as 'partial sight'), is a significant reduction of visual function that cannot be fully corrected by ordinary eyeglasses, contact lenses, medical treatment and/or surgery.

A person with low vision will have some sight but it will be reduced and will usually interfere with everyday activities, such as cooking, reading and writing. If the visual field is reduced, the person may have difficulty seeing well enough to walk alone or drive a car. The World Health Organization defines low vision as visual acuity or worse than 6/18 (US 20/60), but better than 3/60 (10/200 in US terms), or a visual field of less than 20 degrees in the better eye with best correction.

Definition of Best Possible Correction

"Best possible correction" is the best visual acuity achieved with spectacles, contact lenses, and/or surgery. However, when the best possible correction cannot achieve 20/20 or 6/6, the person is said to have "low vision". Low vision causes a significant reduction in visual function that affects daily activities. These people may need additional "low vision aids" such as a special magnifier.