Assessment of visual acuity (VA) has been shown to vary between tests, which may be attributable in part to test inaccuracies, such as a change in the distance between the chart and subject. Therefore ...

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 ...