Cones (color sensitive receptors) containing single visual
pigments selective for red, green, and blue light, are present
in the normal human eye. Disturbances of color vision will occur
if the amount of pigment per cone is reduced or if one or more
of the three cone systems are absent. Although defective color
vision may be acquired as a result of another eye disorder, the
vast majority of color blind cases are hereditary - present at
birth. The gene for this is carried in the X chromosome. Since
males have an X-Y pairing and females have X-X, color blindness
can occur much more easily in males and is typically passed to
them by their mothers. Color blindness is rooted in the
chromosomal differences between males and females. Females may
be carriers of color blindness, but males are more commonly
affected. Color blindness is a malfunction of the retina, which
converts light energy into electircal energy that is then
transmitted to the brain. This conversion is accomplished by two
types of photoreceptor cells