Protanopia

Seeing the world in colors is possible due to the ability of our visual system to perceive light waves of different lengths, corresponding to colors and shades, and transform them into a holistic sensation of a colored picture of the surrounding reality. People who do not distinguish colors are called color blind. This is common knowledge. And protanopia? What is it?

Color blindness or light sensitivity disorder is a collective term. It turns out that there are different ways to not distinguish colors. Complete color blindness, when a person sees the world as if it were a black and white photograph, is called achromasia. This pathology of color vision is rare. More often, a person does not perceive light radiation of a certain range. Protanopia is the absence of perception of the longest waves, perceived as a spectrum of shades of red. Instead, protanopes see gray of varying saturation. Weakening of the perception of shades of red is protanomaly.

The name comes from protium, the lightest isotope of hydrogen, which has a red spectrum of light emission.

This is the most common type of color vision disorder. This is the type of vision disorder that D. Dalton suffered from, who was the first to study and describe it at the end of the 18th century using members of his family as an example. With his light hand, any congenital color vision disorder began to be called daltonism.

The inability to perceive medium-wave radiation (deuteranopia) is quite common – a person does not perceive the green range of shades. Much less common is color blindness in the short-wave range – from blue to violet (tritanopia).

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Epidemiology

The prevalence of color blindness is low, with one in ten thousand people on the planet having a complete lack of color vision. Some deviations in color perception are present in approximately 8% of the planet's population of white males and 0.5% of females. Moreover, three quarters of cases concern not the absence, but a weakened perception of the red or green part of the spectrum.

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Causes protanopias

In most cases, color blind people are born, most often with protanopia. Genetic mutations are associated with the X chromosome. Inheritance occurs from mother to son. In women who have a pair of X chromosomes from their mother and father, vision disorder develops only if both of them have a defect, and this does not happen very often. Basically, when the mother and father are distant, but blood relatives. Men, having received an X chromosome from a mother who carries a defective gene and not having a healthy spare, suffer from various forms of color blindness.

Color blindness is much less common. Acquired protanopia develops in this case more often in only one eye, where the retina or optic nerve was damaged as a result of an illness or injury.

With age, with the development of retinopathy, cataracts or macular degeneration, the perception of the color palette becomes dull.

Other risk factors for the development of secondary protanopia include stroke or coma, Parkinsonism, eye and brain tumors, long-term drug therapy (in this case, the pathology is often reversible), and exposure to toxic chemicals.

Pathogenesis

Color blindness develops when the photosensitive cells of the retina, the cones, are damaged, thanks to which the image we see is transformed into a nerve impulse transmitted to the brain, where a colorful perception of what we see is formed. The cones are responsible for daytime color vision.

At the moment, the three-component hypothesis of our color perception prevails in the theory of vision, according to which the cones of the eye are excited to varying degrees under the influence of light waves of different lengths corresponding to red, green and blue colors. They have such properties due to the content of a biosensitive color pigment in them - iodopsin. According to the three-component theory, it comes in three types: erythrolab is sensitive to red shades, chlorolab is sensitive to green shades, and cyanolab is sensitive to blue shades. Moreover, the first two types have already been discovered, the third is still being sought, but a name has already been invented for it. According to this theory, people with protanopia lack or have very little erythrolab or cones predominantly with this pigment, which does not allow them to distinguish shades in the red part of the spectrum. Accordingly, deuteranopes do not have enough chlorolab.

But there are different interpretations regarding the blindness in the blue part of the spectrum. While supporters of the three-component hypothesis are looking for cyanolab in cones, supporters of another view on the formation of color vision (two-component theory) assume that the cones contain erythrolab and chlorolab simultaneously, and the rods are responsible for the perception of the blue part of the spectrum. The faded pigment rhodopsin, contained in the rods responsible for good vision in the dark, acts as cyanolab. This theory is supported by the fact that people who do not distinguish blue shades also suffer from night blindness, that is, they see poorly in the dark, unlike protanopes and deuteranopes.

In any case, protanopia is related only to photosensitive cells – cones and the deficiency (absence) of the pigment erythrolabe in them.

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Symptoms protanopias

Congenital disorder of color perception, especially partial, is discovered by chance, since it usually does not bother a person in any way. There is no pain, vision is normal, a person sees colors in the distinguishable spectrum the same way from birth and it does not occur to him that someone sees them differently. Of course, if a child constantly draws a gray sun or yellow leaves on trees, it is worth observing him and, perhaps, taking him to an ophthalmologist. Although this may be a manifestation of a child's imagination. By the way, D. Dalton discovered protanopia in himself at the age of 26. Until that time, it did not bother him at all.

Another matter is the acquired lack of color perception; in this case, the patient begins to see colors differently than before, and, naturally, immediately pays attention to this.

Protanopia and deuteranopia are the inability to perceive the red or green part of the color palette. Such dichromacities are among the most common features of color sensitivity. At the same time, a protanope can distinguish green from blue and even from dark red, but cannot distinguish purple (a mixture of blue and red) from blue. To determine the form of color blindness, you need to contact specialists who have color perception testing tools at hand.

Partial anomalies of color vision, when the activity of one of the color pigments is only reduced, are even more common. The most common is deuteranomaly, when the activity of chlorolab is weakened, and a person does not perceive some shades of green, for example, does not see the difference between light green, olive and turquoise, but can distinguish green from red, yellow or blue.

If a person does not distinguish purple from crimson and pink, but sees them as red, that is, still distinguishes the three primary colors, then he most likely has protanomaly - reduced activity of erythrolabe in cones. But, nevertheless, three-color vision is present.

If you have been diagnosed with protanopia, it is unlikely that you will be able to obtain a driver's license even for personal use (without the right to work for hire). In the 21st century, the rules for issuing licenses to people with color vision disorders have become stricter. Even protanomaly is currently an obstacle to obtaining a driver's license. Although the final word is with the ophthalmologist.

To diagnose dichromatic color perception disorders, including such as protanopia, there is the Rabkin test - special pictures with a so-called color code. Normal trichromats have no problem answering the question of what they see in the picture. People with color sensitivity disorders usually fail to discern the coded images in these pictures.

The American military uses Ishihara plates to diagnose color vision disorders. There is also a device for detecting color sensitivity anomalies – an anomaloscope. Such a diagnosis should be made by specialists.

Treatment protanopias

Daltonism (protanopia) as a congenital pathology is incurable. At the modern level of medicine, even the causes of such disorders are still being studied. The acquired defect can be corrected and in some cases eliminated. Treatment and its success depend on the underlying pathology that caused the color perception disorder.

They have not learned to treat congenital pathologies, but they try to help people with color vision disorders. Scientists and doctors are trying to return all the colors of the world to people.

For example, you can enable the color blindness mode "Protanopia" on your computer. This color filter is intended for people who have difficulty distinguishing red and green colors. You can configure them in the "Accessibility" option. When you enable the filter, previously mixed colors become more distinguishable and clear.

In addition, color blind people are prescribed special glasses, and manufacturers position them not just as coloring, but as separating light waves. At first, this optical device was generally recommended as glasses for protanopia, however, they can help with other forms of color perception disorder, and not suit a protanopic. Judging by the reviews, the sensations from the glasses are very individual, so they cannot be called a panacea. The most reputable and expensive brand is Enchroma corrective glasses, a more budget option is Pilestone glasses.

Any glasses need to be tried on, getting used to the lenses does not happen immediately and takes from several hours to several days. About a tenth of users did not recognize any effect from using glasses at all. However, other correction methods for color blind people, except for those listed, have not yet been invented.

In conclusion, I would like to note that many successfully adapt to their vision feature, it does not cause them any trouble. People do not even have an idea about the form of color blindness they have, they just live and do not intend to do anything.

For your information:

Protanopia: Wikipedia (the free internet encyclopedia) briefly and clearly describes this type of color sensitivity disorder in the section on "Color blindness".

The comic strip "Protanopia" was released by a cartoonist from Thailand. A product with moving pictures for iPhones and Internet tablets. The pictures in this application are moving, and not only in a plane, as we are used to seeing in cartoons, but also in three-dimensional space. This is achieved by tilting the device in different directions. Another achievement of computer animation is not a test for color blindness and has no direct relation to this vision pathology.