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Color Blindness in Human

Color Blindness in Human

About one in ten men has some form of color blindness, visual inability to distinguish certain colors, which has a genetic origin linked to chromosome X.

How do we see the colors?

The human eye is formed by different structures which interact to allow the reception of visual stimuli.

One component of the eye is the retina, which is situated in the rear of the eye and is answerable for “project” images (stimuli) to it from the outside. In this part of the eye are the only cells capable of capturing color and light, they are called rods and cones.

There are three types of cones, each of which can capture wavelengths equivalent to red, blue and green, with its pigment content (molecules that capture light at different wave lengths-what amounts to the different colors -). Through the different intensities captured by the three types of cones, one can distinguish all the colors that make up the visible light spectrum.

What is color blindness?

This disorder is named after the English scientist John Dalton, who was the first case of blindness. Color blindness is a visual disability that prevents distinguishes certain colors. This is due to the lack or malfunction of one or more than one type of cone.

There are several variants of this disorder; in fact, it could be said that no colorblind looks exactly like another. Making a classification can roughly distinguish three types of color blindness:


The most common way is Dichromatism, which affects the cones responsible for capturing red or green. In the absence of one of the cell types, the other will pick up the stimuli that correspond to the first; so in many cases the two incoming stimuli will be perceived as the same color. People with this type of blindness have difficulty telling the difference between red and green.

Another variant of this disorder is the lack of cones responsible for capturing the blues; in this case, individuals often confuse blue and yellow. These types of color blindness are called Dichromatism, since the individual has only two types of cones.

Abnormal trichromatism

Another form of color blindness which has similar effects, although milder than previous two cases. In this case, the individual has the three types of cones, but there is some deficiency in the same which prevents complete operation.


Finally, the most serious case of color blindness is called Achromatopsia, as a result of which the individual who suffers appreciates only differences in grayscale.

Causes of blindness

This disorder has a genetic origin; It is a disorder of sex-linked inheritance, that is, the affected gene is located on one of the sex chromosomes (humans have 46 pairs of chromosomes of which 22 pairs are autosomes and one pair is sexual).

In this case it is a recessive X-linked gene; this means that all people who inherit an X chromosome with the defective gene and suffer the disorder than women, however, it will suffer only if both chromosomes present the gene (which is highly unlikely, because it would require both parents portasen this gene). This explains why color blindness is rare in women, while about one in ten men has some form of color blindness.

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