Studies show 5% to 8% of men and 0.5% of women in the world are born colorblind. That is 1 out of 12 men and 1 out of 200 women. Many people think anyone labeled as “colorblind” only see black and white – like watching a black and white movie or television. This is a big misconception and not true. A better term is “color vision deficiency”.
The mechanism of seeing color is as follows:
- The eye perceives light and will stimulate the retina, a lining in the back of the eye.
- The retina consists of “rod” cells and “cone” cells. The rods are useful for night vision, but can not distinguish color, while the cones are not much good at night but do let us perceive color during daylight conditions.
- The cones each contain a light sensitive pigment which is sensitive over a range of wavelengths (each visible color is a different wavelength from approximately 400 to 700 m). Genes contain the coding instructions for these pigments and if the coding instructions are wrong, then the wrong pigments will be produced and the cones will be sensitive to different wavelengths of light (resulting in a color deficiency). The colors that we see are completely dependent on the sensitivity ranges of those pigments.
People with normal cones and light sensitive pigment (trichromasy) are able to see all the different colors and subtle mixtures of them by using cones sensitive to one of three wavelength of light – red, green and blue. A mild color deficiency is present when one or more of the three cones light sensitive pigments are not quite right and their peak sensitivity is shifted. A more severe color deficiency is present when one or more of the cones light sensitive pigments is really wrong.
Understanding the development of the cone cells in the retina, we can say everyone was born color blind since the cones don’t begin functioning until a baby is about 4 months old.
Why does this happen?
Color blindness is almost always hereditary.
Other causes of color blindness include brain or retinal damage caused by accidents, certain drugs, aging process, or certain diseases (i.e. diabetes).
Diagnosis and Types of color blindness
There are several different kinds and degrees of color vision deficiencies.
- Total color blindness
- Partial color blindness
The two major types of color blindness: those who have difficulty distinguishing between red and green, and those who have difficulty distinguishing between blue and yellow, while total color blindness, when someone only can see black and white, is extremely rare.
Diagnosis is done by the color blindness test, where someone reads a plate of colored dots.
Color blindness that is acquired may sometimes be improved by surgery. For example, if you are having trouble seeing colors because of cataracts, surgery to treat the cataracts may improve color vision. If the problem is caused by a side effect of medicine, color vision may be improved when that medicine is stopped.
There may be some things you can do to help compensate for a color vision problem.
- Specially tinted contact lenses and eyeglasses may help you see differences between colors, but these lenses do not provide normal color vision and can distort objects.
- Glasses that block glare (with side shields or wide temples) are helpful because people with color vision problems can see differences between colors better when there is less glare and brightness. A person with color vision problems can actually see better when the lighting is not bright.
- If you do not see color at all and rely on rod cells for vision (rod monochromatism), you may need to wear tinted or dark glasses with side shields because rod cells work better in dim light. You may also need corrective lenses (glasses or contact lenses) because vision using only the rod cells is less clear and sharp.
Color vision problems cannot be prevented.