Colour Blindness
Color blindness is a color vision deficiency where one cannot make out the difference between certain colors. Though most of the times it is caused due to genetic reasons, it may also be the result of eye, nerve, or brain damage, or due to exposure to certain chemicals. The retina of the eyes, in humans, have certain cells that are color sensitive and are necessary for the distinction of red, green and blue colors. These cells are controlled by certain genes, which are located on the X chromosomes of human beings. Men who have the recessive genes of these genes are unable to distinguish the red & green and blue colors and are called color-blind men.
Causes:
Inherited color blindness can be present from birth or may happen during childhood or adulthood due to certain inherited diseases like Cone dystrophy, Cone-rod dystrophy, Blue cone monochromatism, Retinitis pigmentosa, Diabetes, age-related Macular degeneration and Retinoblastoma. The other causes for color blindness can be Shaken Baby Syndrome (which may cause retina and brain damage thus, leading to color blindness), injuries resulting from accidents or swelling of the brain in the occipital lobe as also due to damage caused to the retina by UV exposure.
Some of the facts regarding color blindness can be stated as:
Color blindness is more frequent among men than in women. This is owing to the fact that men inherit only one of the X chromosomes (XY) while women have two (XX) which leaves no extra normal chromosome (x) in males to override the chromosome (the X in the XY set up) which carries the mutation. With rare exceptions color-blind women always have color-blind fathers and the sons of such color-blind women are all color-blind.
Tests for diagnosing color blindness:
Ishihara color test: This is most often used to test red-green color blindness. It comprises of a collection of plates filled with colored dots. The dots are colored in different shades and a number is hidden with shades of another color.
There are also other clinical tests available which are fast, simple, and effective at identifying broad categories of color blindness like Farnsworth Dichotomous Test (D-15), City University Dynamic Color Vision Test to name a few.
