Color blindness

What is color blindness?

Color blindness is a predominantly genetic defect, which consists in the "total or partial inability to distinguish colors due, mainly, to an" alteration of the photosensitive structures in the retina.

Although it is a disorder that involves a small slice of the population (it is estimated that about 8% of men and 0.5% of women are affected by forms of color blindness), it is still a very serious disease, perhaps because it intrigues many people. "Normal" that find inconceivable or at least strange the inability to distinguish colors correctly.
The term "color blindness" comes from the chemist John Dalton who first wrote an article in which he exposed the problem arising from his color blindness.

Common color blindness

The most common form of color blindness is red-green blindness: affected subjects are unable to distinguish the two colors because the wavelengths of red and green, respectively medium (700 nm) and long (540 nm), are perceived as identical. Any green image on a red background (as in the figure), in fact, is not distinct from color blind subjects: strictly speaking, for color blind people a particular combination of colors is indispensable, which excludes the "red-color combination. green.
Color blindness is considered a sex-linked disease, which means that genes located at the level of the X sex chromosomes are responsible for color blindness: the disease, in fact, affects mainly males (XY) and less females (XX).

Genetic causes

We have seen that the gene implicated in color blindness, a recessive disease, is located in the sex chromosome X: this means that color blindness is not transmitted directly from the affected father to the son, but a carrier daughter could transmit the disease to the grandson. To better understand: being an X-linked disease, from a healthy mother and a color blind father, all daughters will have one healthy X chromosome (from the mother) and another defective X chromosome (from the father). For this reason, color blindness is usually passed on to every other generation (from grandfather to grandson). It is rare, but not impossible, for the disease to affect females; if mother and father are color blind, the offspring will also be color blind regardless of sex.

Despite what has been said, it is possible that color blindness can also occur after birth: diseases that affect the eyes, retina, brain, optic nerve and some chemical components, could cause more or less severe forms of color blindness. It should be emphasized, however, that in cases of extra-genetic color blindness the perceived chromatic alteration can be reversible and / or affect only a part of the visual field.

Are there cures?

There are no drug treatments to correct congenital color blindness; the only treatment is of a technological-IT nature. A software suitable for people with color blindness has been programmed to be able to distinguish colors (albeit in a not completely natural way): by moving the cursor over a colored element, the software will indicate the color name.