If there is some problem with the pigments in the cones, the eye will not see colors in the usual way. This is called color deficiency or color blindness.

If just one pigment is missing, the eye might have trouble seeing certain colors. Red-green color blindness – where red and green might look the same – is the most common form of color blindness, followed by blue-yellow color blindness. Patients who have blue-yellow color blindness almost always have red-green color blindness, too.

Rarely, none of the pigments are present in the cones, so the eye does not see color at all. This most severe form of color blindness is known as achromatopsia.

What causes color blindness?
Color blindness is a genetic condition that only rarely occurs in women, but affects one of every 10 men to some degree. When someone is color blind, it is usually because his or her eyes do not make all the pigments needed for color vision.

Does color blindness cause other health problems?
The kind of color blindness that is present at birth does not lead to additional vision loss or total blindness. But because the cone cells of the retina are also used to see fine details, people who are color blind tend to have vision that is less sharp. The rod cells also tend to be "overloaded" by bright light, so tinted eyeglasses often help color blind people to see better.

If you think you have a problem with color vision, you should schedule an appointment with an eye doctor right away. The doctor will be able to tell you whether you are seeing colors properly and what to do if you are not.