A color vision test, also known as the Ishihara color test, measures your ability to tell the difference among colors. If you don’t pass this test, you may have poor color vision, or your doctor may ...

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 ...

The expression of five major families of visual pigments occurred early in vertebrae evolution, probably about 350-400 million years ago, before the separation of the major vertebrate classes.

Acuity of vision is a term used to describe the clearness or sharpness of your vision when measured at a distance of 20 feet. ‌ Visual acuity is the most common clinical measurement of how your eyes ...