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 ...

What does 20/20 vision mean? When you visit your doctor or an eye care professional, you may be asked to read an eye chart. You may be told you have normal 20/20 vision. What does that really mean? An ...