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 ...

Our ability to see with color vision depends on the presence and function of light-sensing pigments in the cones of our eyes. Color blindness, or color vision deficiency, happens when one or more of ...

Red-green color blindness is the most common type of color deficiency. Also known as deuteranopia, this is most likely a congenital condition, meaning that you’re born with it. If you have this type ...