The term "20/20 vision" refers to how sharp your eyes are when you look at a standard eye chart (Snellen chart) from a distance of 20 feet (or 6 meters)—depending on where you live. In the United ...

"This study aimed to evaluate the equivalence of a smartphone-based visual acuity chart with a standard 6-m Snellen visual acuity (6SVA) chart." Researchers first reviewed Snellen chart apps that were ...

Impaired vision and blindness are common. About 3.4 million people in the US are blind or visually impaired. Vision is usually measured by visual acuity charts, and normal vision is expressed as 20/20 ...