What determines the color of the human eye. Changing the color of the iris

It often happens that a child is born with light eyes (light blue or light green), but over time they darken and become dark gray or even brown. Let's see if this is normal? And why do people have different eye colors?

The color of the skin, hair and eyes of a person depends on the content of the melanin pigment. He absorbs ultra-violet rays and protect us from radiation damage. That is why fair-skinned people burn faster in the sun than dark-skinned people: there is less pigment in their skin. The color of the iris of the eye also depends on the content of melanin, as well as on the density of the fibers of the iris.

The main eye colors are blue, blue, gray, green, amber, swamp (walnut) and brown.

In the owners of blue and blue eyes, the content of melanin in the iris is the smallest, in the owners of brown eyes - the highest. The proverbial black eyes are the eyes dark brown. Albinos have red eyes, this is due to the fact that there is no melanin in their body at all, so the color of the iris is determined by the color blood vessels.

Eye color (or rather, the amount of melanin) is a genetically determined trait. Dark eye color is dominant and light eye color is recessive. dark eyes occur more frequently. The most common eye color in the world is brown, and the rarest is green. Another eye color depends on the region of residence - in different peoples different frequency distribution of certain eye colors.

Let's say if among the Russians Brown eyes have about 30% of people, then among Ukrainians - already 50%, and among Hispanics this figure reaches 80%. Of course, this is a simplified scheme, the inheritance of eye color is much more complicated, but in any case, a brown-eyed child cannot be born to light-eyed parents (but on the contrary, it is quite possible). You can determine what color a child's eyes will be based on the color of their parents' eyes. But in most cases, several options are possible with different probabilities, so it is most accurate to predict final result maybe only for a child of two blue-eyed parents.

But even if a child was born with light eyes, it is not necessarily forever. Over time, the color of the eyes in newborns may change. This is due to the fact that special cells (melanocytes) do not immediately begin to produce melanin, and the accumulation of pigment in body goes gradually. A child born with gray eyes may well become brown-eyed over time. Eyes can finally take normal color and in six months, and in a year, and even in two or three years.

It is worth remembering that the eyes can turn from light to dark, but from dark to light - not (unless a failure occurred in the child's body that disrupted the production of melanin).

It also happens that the eyes have different colour: one is colored stronger, and the second is weaker. This phenomenon is called heterochromia, and it is associated with a relative excess or deficiency of melanin. There is also partial (sectoral) heterochromia, when parts of the iris of one eye are colored differently, but this is a rarer phenomenon than complete heterochromia. Heterochromia can be caused by various reasons. Sometimes, in addition to changing the color of the iris, it does not manifest itself in any way, and sometimes it can be accompanied by complications up to cataracts. Therefore, people with heterochromia should be regularly observed by an ophthalmologist.

From school course biology, we know how the eye color of a child is genetically determined, we are aware that brown color dominates over blue and it happens that a person has eyes of different colors. We will tell you about the facts that you did not know. For example, until what age is eye color formed and why does our iris have one color or another?

Fact 1: all people are born with bright eyes

Please note that all newborn babies have gray-blue eyes. Ophthalmologists explain this very simply - babies have no pigment in the iris. Exceptions are only in the countries of East, Southeast and South Asia. There, in children, the iris is already saturated with pigment.

Fact 2: we acquire the final color of the eyes in adolescence

The color of the iris changes and forms by 3-6 months of a child's life, when melanocytes accumulate in the iris. The final color of the eyes in humans is established by 10-12 years.

Fact 3: brown eyes are blue eyes

Brown is the most common eye color on the planet. But ophthalmologists say that brown eyes are actually blue under brown pigment. This is the result of a genetic mutation. The outer layer of the iris contains a large number of melanin, resulting in the absorption of both high-frequency and low-frequency light. Reflected light results in a brown (brown) color.

Exists laser procedure, which allows you to remove the pigment and make the eyes blue. It is impossible to return the previous color after the procedure.

Fact 4: in ancient times everyone was brown-eyed

Researchers have found that 10 thousand years ago, all the inhabitants of the planet had brown eyes. Later, a genetic mutation appeared in the HERC2 gene, in carriers of which the production of melanin in the iris decreased. This first led to the emergence blue color. This fact was established by a group of scientists at the University of Copenhagen led by Associate Professor Hans Eiberg in 2008.

Fact 5: a little about heterochromia

This is what is called the different color of the iris of the right and left eyes or the unequal color of different parts of the iris of one eye. This feature is explained by the fact of excess or deficiency of melanin due to diseases, injuries, genetic mutations. With absolute heterochromia, a person has two different colors of the iris. One eye can be blue, the other brown. The planet is home to 1% of people with such an unusual deviation.

Fact 6: green is the most rare color eye

Green eyes have 1.6% of the people of the planet, it is the rarest, as it is eradicated in the family by the dominant brown genome. Green color is formed like this. In the outer layer of the iris, an unusual light brown or yellow pigment lipofuscin is distributed. Together with the blue or blue color turns green. Purely green color the eye is extremely rare: the color of the iris is usually uneven, and this leads to the appearance of numerous shades. Most often, green eyes are found in those whose genotype is dominated by the gene responsible for the red hair color. Swiss and Israeli scientists came to such conclusions. These findings are indirectly supported by the high prevalence of green eyes among red-haired people. The results of the study are published in the section " genetic nature» Portal Nature.com (Nature.Com).

Fact 7: a little about other colors of the iris

Black color the eye is similar to the structure of brown. But the concentration of melanin in the iris is so high that the light falling on it is actually completely absorbed. Black eye color is most common among representatives of the Mongoloid race in East, Southeast and South Asia. In these regions, the iris of newborns is already saturated with melanin.

Blue color the eye is the result of light scattering in the stroma (in the main part of the cornea). The lower the density of the stroma, the more saturated Blue colour.

Blue eye, unlike blue, is explained more high density stroma. The higher the fiber density, the lighter color. As we all remember, this beautiful color was partly the reason for the formation of fascist ideology. After all, according to scientists, 75% of the indigenous people of Germany have blue eyes. No other country in the world has such a concentration blue-eyed people.

hazel color is a combination of brown (hazel), blue or light blue. And it can take on different shades depending on the lighting.

Grey colour the eye is similar to blue, while the density of the fibers of the outer layer is higher. If the density is not so high, the eye color will be gray-blue. Gray eyes are most common in northern and eastern Europe, certain regions Northwest Africa, as well as among the inhabitants of Pakistan, Iran and Afghanistan.

Yellow eyes are extremely rare. It is formed due to the content of the pigment lipofuscin (lipochrome) in the vessels of the iris. But in most cases, the fact of this eye color is due to the presence of kidney disease.

Fact 8: Albinos can have both red and purple eyes.

most unusual and interesting color eye, red, commonly found in albinos. Due to the lack of melanin, the albino iris is transparent and appears red due to the blood vessels. In some cases, red, mixing with the blue color of the stroma, gives purple eye. However, such deviations occur in a very small percentage of people.

Prepared using materials: ailas.com.ua, medhome.info, glaza.by, medbooking.com, nature.com, nfoniac.ru

It is very interesting to know what eye color depends on. After all, the variety of colors of human eyes is amazing and makes you wonder how it arose in nature.
What is commonly called "eye color" is nothing more than the color of the iris, the pigment cells contained in it give the eye color: more pigment - darker color and vice versa.

What determines eye color and what factors affect it

What determines the color of a person's eyes?

Albinos lack melanin, so their eyes look reddish (blood vessels show through the translucent iris).

Scientists have found that people have different densities of the fibers that make up the iris.

This feature also affects the color of the eye. The denser the fibers that form the iris, the lighter its shade. The back layer of the iris is always dark, even in light-eyed people.

The blue color of the eyes is due to the low content of melanin and the low density of the fibers of the iris.

Blue eyes mean that the fibers that make up the iris are denser. Their color may be close to white or gray.

In gray eyes, the fibers in the iris are even denser than in previous cases. The gray-blue tint of the eyes is formed due to the fact that this density is slightly less high.

The green color of the eyes means that the amount of melanin in the iris of their owner is small. It is known that green is formed by mixing blue and yellow. The pigment lipofuscin just has a yellow color and, superimposed on melanin, gives the eye a green color.

An amber or golden color is also formed due to high content in the iris of the yellow pigment lipofuscin.

Brown and black color are obtained due to the high content of melanin in the iris. Black-eyed people have so much of it that the iris completely absorbs the color falling on it.

The color of the iris is acquired by the child from the father and mother, and the genetics of the eye color is difficult to predict. There are thousands of color combinations for children and parents.

From school textbooks, we all remember that the genes responsible for dark color, are dominant. The traits that they determine always "win" over those traits that are encoded by the genes responsible for the light shade.

However, all this does not mean that brown-eyed men and women will necessarily have brown-eyed children. Such a couple may also have a blue-eyed child, if one of the grandparents has a different eye color. A baby can get a recessive gene from one of the parents.

Eye color perception

The eye can be compared to a camera, because it also has its own light-sensitive layer - the retina. Nerve cells The retinas receive reflected light and transmit sensations to the brain.

In the human mind, an image of the surrounding world arises due to the processing of signals supplied to the brain by eye cells - rods and cones. The former are included in the work at dusk, the latter are responsible for the perception of color.

For a person there is no objective and pure perception of color. This process is not only physical, but also psychological. Perception is always influenced various factors: background, environment, shape of the object. For example, if a yellow object is placed on an orange background, it will appear colder, greenish.

Under different lighting conditions, a blue object may appear either black or purple. In the dark, all objects appear black.

Thus, the color of things is not a permanent and inalienable property of them, like, for example, shape and weight. In addition, individual characteristics of a person affect the perception of color: age, eye health, emotional state.

It is almost impossible to see the color of an object in its “pure” form, but the most “correct” idea of color can be obtained by looking at the object in daylight, without bright sun.

Dependence on blood type

From the moment that humanity became aware of the existence of blood groups, people have been wondering if there is a connection between the blood group and other characteristics of a person ( appearance health, character).

You may have come across statements that among the carriers of the first and second blood groups, there are most blue-eyed blondes, representatives of the third group are swarthy and black-eyed, and the fourth group is mixed.

Such hypotheses have not received scientific confirmation. The fact is that the genes that determine the blood group and the genes responsible for eye color are not related, they are on different chromosomes. They cannot interlock with each other in the process of inheritance.

In addition, the possession of a certain blood type does not directly depend on belonging to a race or ethnic group, although blood groups are indeed unevenly distributed among different nationalities.

For example, 8 out of 10 American Indians have the first type of blood, and the inhabitants of the northern part of Europe most often have the second type.

However, there are no distinguishing external features in people with a particular blood type or Rh factor. Therefore, it is impossible to predict eye color based on a person's blood type. You cannot even calculate the probability that a person with a particular eye color will have a certain blood type.

The influence of a person's nationality

We easily notice a person of a different nationality due to special features of appearance, and eye color is not the last in the list of such features. Most of the world's population has dark skin and black or brown eyes.

The appearance of Europeans is very diverse: they can be with blue eyes, brown, green, and the inhabitants of the northern and of Eastern Europe lighter on average.

The most rare eye color is green, only 2% of people have green eyes. green eyed people are found among the Western Slavs, as well as some eastern peoples.

Quite a lot of them among the Germans and Swedes. By the way, there are unusually many green-eyed and blue-eyed people in Iceland - 80% of the population. In Turkey, only 20% of green-eyed people.

The most common eye color on Earth is brown, because its carriers are the vast majority of the inhabitants of India and China. The prevalence of brown color is also explained by the fact that this is the most “useful” color of the iris: dark eyes are not afraid of the bright sun. The peoples of the north, who have to watch the blinding glare of snow, also have dark eyes.

About half of Russians have gray eyes and brown, blue and blue are less common (about 20%). In the northern part of the country, a gray-green eye color is common.

Useful video on the topic

Color change options

The color of the eyes of adults can change under the influence of a variety of factors. There is even such a thing as "chameleon eyes". Their color is difficult to determine, as it constantly changes under the influence of lighting and furnishings.

There are several reasons why a person's eye color changes:

Age changes. It is noticed that the color of the eyes can change as in childhood(up to two or three years it is unstable), and in old age. In older people, the pigment begins to be produced in a smaller volume, the eyes may become slightly lighter. For some, they, on the contrary, darken due to the fact that the iris loses its transparency.
Time of day changes. The eyes change their color during the day. Of course, this phenomenon has nothing to do with pigmentation, it's a matter of our perception of color, which can be influenced by lighting and environment. Moreover, in response to bright lighting the pupil constricts and the eye appears brighter. In the dark, the icon expands and even light eyes may appear almost black.
After tears. It can be noticed that after prolonged sobbing, a person acquires not only a red face, but also a brighter than usual eye color. Most likely, such changes are related to the fact that the eye receives good hydration, the protein becomes lighter, and the iris stands out more against its background.
Disease. In some diseases (glaucoma, Horner's syndrome, Fuchs' dystrophy), changes in eye color can be observed.

Basic color options

A few decades ago, change the color of the eyes, given by nature, was impossible. To date, several ways have been invented to change the color of the iris.

If you are unhappy with the color of your eyes, want to experiment with your image, or want to eliminate a defect such as heterochromia, you have such an opportunity.

Laser eye color correction

Laser technology for changing eye color was developed by California doctor Greg Homer. The doctor has been working on his invention for ten years, and now twenty seconds are enough to change your eye color forever.

By the way, this procedure is irreversible. If you changed your brown color of the iris to green, it will no longer be possible to return your native brown.

The essence of the procedure is that laser ray destroys the thin pigment layer of the eye. The cost of such an operation will be about five thousand dollars, and possible side effects not yet sufficiently studied. Ophthalmologists warn that this procedure can cause vision problems.

Artificial iris implantation

This is an invention of the American surgeon Kenneth Rosenthal. He developed the technology of changing eye color by inserting into the cornea silicone implants. This procedure can also be hazardous to health.

The first two months after the operation will be spent on restoring vision, and in the future, the chances of developing such serious illnesses like cataract, glaucoma, corneal detachment. If you decide to change your eye color in this way, you run the risk of permanent blindness.

Rosenthal himself did not initially plan that the procedure he invented would be used for everyone. His mission was to treat birth defects eye. However, some private US clinics still adopted this method and actively apply it.

Special eye drops

A darker shade of the eyes can be obtained if certain types are used for a long time. eye drops. These drops contain an analogue of the hormone prostaglandin F2a, which can affect the color of the iris.

This method of changing eye color can again be harmful to health, as it involves the use medical preparations not prescribed by a doctor. With regular use of eye drops, nutrition is disturbed eyeball.

Contact lenses

It is the most popular, inexpensive and safe way change eye color. However, it will not be superfluous to still seek advice from an ophthalmologist who will help you choose lenses according to the characteristics of your eyes and your vision.

Lenses are tinted and colored. The former change the color of the eyes slightly, the latter will help to change it radically.

If you have light eyes, any kind of colored contact lenses will work, but dark-eyed people will have a little more difficulty, because tint lenses on dark eyes will not be visible. Also, when purchasing tinted lenses, keep in mind that your original eye color will blend with the lens color and create a new tint.

Well-chosen makeup

Slightly change the color of the eyes can and matched properly makeup. Using contrasting shades of eyeshadow, you can emphasize the natural color of the eyes, make it brighter and more saturated.

Cold shades of shadows will suit brown eyes, warm shades - blue, and grey eyes can be made slightly green or blue with the help of appropriate shades of shadows.

Causes of heterochromia

Unusually look people whose eyes are of different colors. Heterochromia is the name of the phenomenon in which differences in eye color are observed. There are two varieties of this mutation: complete (the irises of the left and right eyes have a different color) and partial (colored spots or colored areas on the iris of one eye).

This feature is found not only in humans, but also in many species of animals. For example, there are many “odd-eyed” among cats, among husky dogs, as well as horses and cows. Usually it is combined with a piebald or marble color. In humans, heterochromia is much less common than in animals (10 cases out of 1000).

Heterochromia does not affect health and vision in any way. This is just an abnormal pigmentation of the eye, associated with an excess or lack of melanin. Most often, this feature is inherited from parents, but in rare cases May be the result of injury or illness. For some reason, heterochromia is more common in women than in men.

If heterochromia is not caused by a disease or damage to the eye, it does not need treatment, and it is unlikely that it will be possible to change the color of the eyes forever. Can you hide heterochromia? contact lenses, but usually there is no urgent need for this. People with eyes of different colors are considered by many to be pretty, so their peculiarity is perceived not as ugliness, but as a kind of "zest".

It is worth noting that heterochromia is gradually coming into fashion. Someone creates such a “mutation” artificially for himself by putting on lenses, and teenagers often wonder how to get heterochromia.

Eye color formation

It has been observed that most newborns differ light color eye. The fact is that melanin occurs in the body under the influence of light. Since there is no light in the mother's womb, melanin is not yet released in the child's body. Only after birth, the amount of melanin in the baby's eyes will gradually accumulate.

What determines the color of a child's eyes?

It is possible to determine the future eye color of a child using special plates that are published in magazines and in social networks. predict it with one hundred percent certainty impossible, because not only mom and dad, but also grandparents make their contribution to the color of the baby's eyes.

There is no such specialist who could satisfy the curiosity of parents and determine in advance what the color of the eyes of an adult crumb will be.

baby color change

Parents eagerly wait for the moment when their baby will have the “final” eye color and argue about which of the relatives he was transmitted from.

In the early days, the shade of the baby's eyes is still too early to compare with the parent, heredity will manifest itself a little later. Most babies are born with light blue or light green eyes, and their hue may change during the first years of life.

On average, the first changes occur at about three months of age. A gray-eyed baby can eventually become green-eyed, and then brown-eyed. In some babies, eye color changes a few months after birth, and six months later, and a year.

Only at the age of two or three years does the baby acquire a “settled” eye color. Of course, there are exceptions to this rule - in some children, already in the first months of life, permanent color eye. Usually these are swarthy and dark-eyed babies. It also happens that the baby is born already with dark eyes.

It is also worth noting that the baby's iris cannot become lighter over time, only darker. After two to three years, healthy eye color little man cannot change drastically, but small changes in their shade sometimes occur.

Find out what determines the color of the eyes

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4.12.2016 00:51

Eye color has great importance in a girl's life, even if we don't think about it.
Very often, clothes, accessories and makeup are matched directly to the color of the eyes, not to mention the fact that, thanks to existing stereotypes, we, to some extent, form our initial opinion about a person, taking into account the color of his eyes.

The color of a person's eyes, or rather the color of the iris, depends on from 2 factors:
1. Density fibers iris.
2. Distribution of melanin pigment in the layers of the iris.
Melanin- a pigment that determines the color of human skin and hair. The more melanin, the darker the skin and hair. In the iris of the eye, melanin varies from yellow to brown to black. In this case, the posterior layer of the iris is always black, with the exception of albinos.
Yellow, brown, black, where do the blue, green eyes come from? Let's take a look at this phenomenon...

Blue eyes

The blue color is obtained due to the low density of the fibers of the outer layer of the iris and the low content of melanin. In this case, low-frequency light is absorbed by the back layer, and high-frequency light is reflected from it, so the eyes are blue. The lower the fiber density of the outer layer, the richer the blue color of the eyes.

Blue eyes

A blue color is obtained if the fibers of the outer layer of the iris are denser than in the case of blue eyes, and have a whitish or grayish color. The greater the fiber density, the lighter the color.

Blue eyes in babies
There is an opinion that all children are born blue-eyed, and then the color changes. This is a wrong opinion. In fact, many babies are actually born light-eyed, and subsequently, as melanin is actively produced, their eyes become darker and the final color of the eyes is established by two or three years.

Grey colour it turns out like blue, only at the same time the density of the fibers of the outer layer is even higher and their shade is closer to gray. If the density of the fibers is not so high, then the color of the eyes will be gray-blue. In addition, the presence of melanin or other substances gives a slight yellow or brownish impurity.

Green eyes

This eye color is most often attributed to witches and sorceresses, and therefore green-eyed girls are sometimes treated with suspicion. Only green eyes were obtained not due to witchcraft talents, but due to a small amount of melanin.
In green-eyed girls, a yellow or light brown pigment is distributed in the outer layer of the iris. And as a result of scattering by blue or cyan, green is obtained. The color of the iris is usually uneven, there are a large number of different shades of green.

Amber

Amber eyes have a monotonous light brown color, sometimes they have a yellowish-green or reddish tint. Their color can also be close to marsh or golden, due to the presence of the pigment lipofuscin.

Brown eyes

Brown eyes are the result of outer layer The iris contains a lot of melanin, so it absorbs both high-frequency and low-frequency light, and the reflected light in total gives brown. The more melanin, the darker and richer the eye color. Brown eye color is the most common in the world.
Black eyes
The black color of the eyes is essentially dark brown, but the concentration of melanin in the iris is so high that the light falling on it is almost completely absorbed.

Red colored eyes

Yes, there are such eyes, and not only in the movies with vampires and ghouls, but also in reality! Red or pinkish eye color is found only in albinos. This color is associated with the absence of melanin in the iris, so the color is formed on the basis of the blood circulating in the vessels of the iris.

purple eyes

The most unusual and rare eye color is rich purple. This is extremely rare, perhaps only a few people on earth have a similar eye color, therefore this phenomenon little studied, and on this account there are different versions and myths that go far into the depths of centuries.

Eyes of different colors

This phenomenon is called heterochromia, which in Greek means "different color." The reason for this feature is the different amount of melanin in the irises of the eye. There is complete heterochromia - when one eye is of the same color, the second is different, and partial - when parts of the iris of one eye are of different colors.

Can eye color change throughout life?

Within the same color group, color can change depending on lighting, clothing, makeup, even mood. In general, with age, the eyes of most people brighten, losing their original bright color.

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The human eye consists of the eyeball and accessory organs. The apple has a spherical shape and is located in the cavity of the orbit.

The middle shell of the eyeball is rich in blood vessels and itself consists of three parts: the anterior (iris) or iris (in the form of a flat ring with a pupil), the middle (eyelashes), and the posterior (cluster of vessels and nerve fibers).

Color human eye determined by the color of the iris. Its shade, in turn, is determined by the amount of melanin in the anterior layer of the iris (the posterior layer has a dark pigment; albinos are an exception) and the thickness of the fibers.

It happens that eye color changes throughout life, you can read about it.

Primary colors of the human eye

Melanin affects the color of the iris of the eyes, hair and skin.

Melanin affects the shade of not only the iris, but also hair and skin. The more it is contained in the body, the more “east” a person looks, that is, melanin colors brown, black, brown.

Brown is the most common eye color in the world. The iris contains a large amount of melanin, the fibers are quite dense.

The prevalence of this shade is explained by its “usefulness”: dark eyes resist both the bright light of the sun (among the southern peoples) and the blinding glare of snow and glaciers (among the peoples of the north).

As a result of evolution and migratory movements, which took place most actively from the 1st to the 5th century AD, this eye color is found on all continents and in all races.

Blue

WITH scientific point vision, blue eyes does not exist. The appearance of this shade of the iris is due to a small amount of melanin and a high density of stroma fibers ( connective tissue). Since it has a bluish color, light reflects off of it and makes the eyes blue. The higher the density of collagen fibers, the lighter the shade.

The decrease in melanin production in blue-eyed people is due to a genetic mutation that is 6-10 thousand years old. This eye color is most common in Europeans.(about 60% of the population), however, it is also found among Asian peoples. In Jews, the birth rate of blue-eyed children is more than 50%.

The blue color of the eyes indicates a small amount of melanin and a low density of stromal fibers. The lower this density, the richer shade. Mostly babies have such eyes.

Gray eyes are similar to blue, but the eyes gray color the density of the fibrous body of the stroma is slightly higher. The shade of gray will depend on the degree of light scattering. At elevated content melanin, yellow or brown pigment spots are possible.

This eye color is most common in Europe and countries such as Afghanistan and Pakistan.

marsh

Swamp eye color - mixed. Depending on the lighting, it appears brown, hazel, golden or green. The number of melanin cells that give Brown color, is small, the admixture of blue or gray depends on the thickness of the stroma fibers.

Usually, the iris of swamp eyes is heterogeneous; there are a large number age spots. You can meet such eyes among the Indians, Europeans and the peoples of the Middle East.

The green iris contains a small amount of melanin; the light brown or ocher pigment of such an iris merges with the scattered blue tint of the stroma and turns green.

Like marsh eyes, green eyes do not have an evenly distributed tint.

Pure green is very rare, is more common in residents of all regions of Europe. According to recent studies, mostly women are born with eyes of this color.

According to some reports, the so-called the red hair gene is a recessive gene in the human genotype.

Black eyes are similar in structure to brown ones, but the amount of melanin in the iris of such eyes is very large, falling on the iris sunlight absorbed almost completely.

Such eyes are common among the peoples of Asia.. Babies in such regions are immediately born with melanin-saturated eye membranes. Pure black eye color occurs in albinism (with the oculocutaneous type).

rare eye colors

The unusual color of the iris is usually caused by various violations: genetic mutations or other failures in normal operation organism.

Red eyes are found in albinos (ocular type of albinism). There is no melanin in the iris of such people, both in its outer layer and in the inner one (which, as mentioned above, has a dark color). The color of the eyes in this case is determined by the blood vessels.

In extremely rare cases, the red color may take on a purple hue due to the blue color of the stroma, but this phenomenon is practically not found. Albinism is only 1.5% of the total population of the Earth. Often accompanied by visual impairment.

violet

The phenomenon of lilac eyes is practically not studied. It was called the "origin of Alexandria": according to the ancient Egyptian myth, the inhabitants of a small village saw a strange flash in the sky and considered it a sign of God. In that year, the women of the settlement began to give birth to children with unusually beautiful eyes.

One of the first was the girl Alexandria: in the first year of her life, her eyes changed from blue to purple. Subsequently, her daughters were born, and each of them had the same eyes. The brightest example a person with such a pathology is Elizabeth Taylor: her iris had a lilac hue. People with this eye color are even rarer than albinos.

Lack of iris

The phenomenon in which the iris is completely absent is called aniridia. It can be caused by deep trauma to the eye, but the most common is congenital aniridia, which is the result of a gene mutation.

People with this pathology have black as coal eyes. As a rule, the mutation is accompanied by visual impairment: hypoplasia, etc.

Eyes of different colors

One of beautiful mutations eyes are considered heterochromia. It is characterized different color irises of the left and right eyes or unequal color of different parts of one eye, that is, it can be complete and partial.

There is both congenital and acquired heterochromia.

She may develop as a result of serious diseases or injuries of the eye(siderosis, tumors). Partial heterochromia is much more common, even in apparently healthy people.

In animals (dogs, cats) this phenomenon is much more widespread than in humans (white cats, huskies, etc.).