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 ...

At least once in your life, you must have squinted at the eye chart at the doctor’s office or DMV, trying to make out the blurry bottom line. The test seems simple enough, right? Read a random string ...