Colour Blindness

What is colour blindness?
In the retina at the back of the eye there are two types of cells, ‘rod cells’ and ‘cone cells’, and these reactdifferently to light. Rod cells are very sensitive to light and they can react to even very faint light, such as light from a star in a hazy night sky, but they do not ‘see’ different colours. Using rod cells we can see things around us at night, but only in shades of black, grey and white.Cone cells react to brighter light and they help us to see the detail in objects. They also pick up colours.

There are three types of cone cells: ones that pick up red light, others green and others blue. By combining the messages from each set of cone cells, we get the
wide range of colours that we can normally see. Someone who is colour blind
lacks one or more of these types of cone cells.

Color blindness affects a substantial portion of the human population. Protanopia and deuteranopia, the two most common forms of inherited color blindness, are red-green color vision defects caused by the absence of red or green retinal photoreceptors, respectively. In individuals of Northern European ancestry, as many as 8 percent of men and 0.5 percent of women experience the common form of red-green color blindness3. If a submitted manuscript happens to go to three male reviewers of Northern European descent, the chance that at least one will be color blind is 22 percent.

Color blindness deficiency is the inability or decreased ability to see color, or perceive color differences, under lighting conditions when color vision is not normally impaired. “Color blind” is a term of art; there is no actual blindness but there is a fault in the development of either or both sets of retinal cones that perceive color in light and transmit that information to the optic nerver.

Color blindness can be diagnosed by self detection. Meanwhile, achromatopsia can be diagnosed only at the age three or four. The simplest way to diagnose this condition is through a color test. Electroretinograph is also used at times.

The symptoms of color blindness may vary from person to person. The symptoms are not very pronounced and the color vision problem is not so severe that the individual gets to know about his disorder. Often, such people who are partially color blind may not realize that they are suffering from color blindness or that they are seeing things differently from what appears to other people with normal color vision. The worst part about this disorder is that there is no cure or treatment plan for it till date.

The symptoms of color blindness also can be produced by physical, chemical damage to the eye, optic nerve, or the brain generally. These are not true color blindness, however, but they represent conditions of limited actual blindness. Similarly, a person with achromatopsia, although unable to see colors, is not “color blind” per se but they suffer from a completely different disorder, of which an atypical color deficiency is only one manifestation.

Health Conditions