Iris – it is a thin movable diaphragm with a pupil in the center. She almost impenetrable, located behind the cornea and in front of the lens, between the front and rear chambers of the eye. The envelope contains the melanocytes (pigment cells), the radial muscles widening the pupil, and circular, narrowing it.
The color of the iris depends on the amount of pigment and blood vessels. Pigments can talk about any disease, such as yellow or brown pigment occurs in diseases of the liver. The colors of natural pigments depends on genes, ethnicity, race.
Iris color is determined by mixing the color of blood in the vessels and mixing color pigments, for example, green is a mixture of yellow and blue. Yellow eyes people have no, but if the blood vessels of the iris is pale in color, it can turn a yellow-green color. If the concentration of melanin the iris gets black tint, gray is a variation of blue.
It happens that a person’s eyes different colors. This phenomenon is called heterochromia. The difference in color appears due to the shortage (excess) of melanin. This phenomenon occurs both in humans and in animals (cats).
Heterochromia is of two kinds: full and partial. Complete heterochromia occurs in cases when the color of the iris is completely different from the color of the «iris» of the other eye. Partial heterochromia is very rare, about 4 people out of 1 million, then one part of the «iris» is different from the remaining part, i.e. one eye combines the two colors.
Heterochromia occurs after fertilization of a cell, it has no effect on human health. People with this phenomenon see and perceive everything around it, like all the others. Most often it occurs in women than in men. There were times that heterochromia was acquired due to illness or injury (waardenburg syndrome or Hirschsprung’s disease).
People with heterochromia get some flavor, among them many famous and popular singers, Actresses: Kate Bosworth (pie hateframe), David Bowie (pseudoliterary due to injury), Christopher Walken, etc.
What our eyes have different color, everyone knows. But not everyone understands why this is so. The fact that the color of our eyes is responsible for the pigment melanin contained in the iris of the eye. The more of his body, the darker the iris. That is, if a person has completely black eyes, so he has a lot of melanin, if a blue or green – a little.
It happens that a person’s eyes different colors. This phenomenon is called heterochromia. The difference in color appears due to the shortage (excess) of melanin. This phenomenon occurs both in humans and in animals (cats). Heterochromia is of two kinds: full and partial. Complete heterochromia occurs in cases when the color of the iris is completely different from the color of the «iris» of the other eye. Partial heterochromia is very rare, about 4 people out of 1 million, then one part of the «iris» is different from the remaining part, i.e. one eye combines the two colors.
Generally eye color is largely determined by heredity. It is known that the Earth is more dark-eyed people, since a large amount of melanin is the dominant characteristic and, therefore, often inherited. So if one parent has brown eyes and the second blue or green, the probability that the child will be blue-eyed are at a minimum.
It is also interesting that the color of the eyes change during life. All children are born with blue eyes – in their body yet not enough melanin. When the pigment accumulates, they become the desired color. To old age some people eyes can become bright due to the fact that the mesodermal layer becomes less transparent.
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The amount of melanin in the iris determines whether we have blue, green, hazel or brown eyes. Blue eyes have the least amount of melanin in the iris; brown eyes have the most. People with different eye colors are rare as well as the reasons that cause this condition.
Heterochromia means “different (hetero) color (chromia)”. Usually the terms is used to describe the condition where a person has different colored eyes – one blue eye and one brown eye, for example.
Heterochromia usually is benign. In other words, it is not an eye disease, and it does not affect visual acuity.
Benign heterochromia can give a person a captivating, even exotic, appearance.
Types Of Heterochromia
There are three types of heterochromia, based on where the different colors are located:
1. Complete heterochromia. This is where the iris of one eye is a completely different color than the iris of the other eye.
2. Partial heterochromia (or sectoral heterochromia). This is where only a portion (or sector) of the iris of one eye has a different color than the rest of the iris of that eye. Partial heterochromia can occur in one eye or both eyes.
3. Central heterochromia. In this type of heterochromia, the iris has a different color near the border of the pupil (compared with the color of the rest of the iris), with spikes of the central color radiating from the pupil toward the middle of the iris.
Something that’s often confused with heterochromia is a benign growth called an iris nevus. A pigmented nevus in the iris usually is round in shape and brown in color. Usually, only one iris nevus is present, but it’s possible to have more.
Though a person might argue that a brown iris nevus on a blue, green or hazel eye is a type of partial heterochromia, the term heterochromia usually isn’t used when the cause of the color variation in the iris is a nevus.
Iris nevi (plural of nevus) typically remain stable in size. If you have an iris nevus, your eye doctor usually will want to see you every six months (for a while, at least) to measure its size and rule out any growth that could indicate malignancy.
Heterochromia also occurs in animals. Breeds of dogs that commonly exhibit heterochromia include Siberian husky, Australian shepherd, collie.
What Causes Heterochromia?
As already mentioned, most cases of heterochromia are benign. An infant can be born with benign heterochromia, or it can become apparent in early childhood as the iris attains its full amount of melanin. These types are called congenital heterochromia.
Usually, congenital heterochromia is a genetic trait that is inherited. Benign heterochromia also can occur as the result of a genetic mutation during embryonic development.
In some cases, heterochromia is a symptom of another condition that’s present at birth or develops shortly thereafter.
One example of a condition that causes heterochromia is Horner’s syndrome. This is the combination of a constricted pupil, partial ptosis and loss of the ability to sweat on half of the face, all caused by an interruption of certain nerve impulses to the eye.
Heterochromia that develops later in life is called acquired heterochromia. Causes of acquired heterochromia include eye injuries, uveitis and certain glaucoma medications.
Have an eye exam to be safe
Though most cases of heterochromia are congenital and benign, if you or your child has different colored eyes (or different colored segments of one or both eyes), see ophthalmologist for a comprehensive eye exam to rule out other causes.
After your doctor confirms your eyes are healthy, enjoy the compliments you are likely to receive about the unique appearance of your two different colored eyes.
The instance of a person having two differently colored eyes is pretty uncommon, just 11 out of every 1,000 Americans. This uncanny trait is caused by several factors, and can actually develop over time.
Iris color develops during the first few months after birth, with the levels of the pigment melanin determining how dark eyes will become. The less melanin expressed in the iris, the lighter a person’s eyes look, and vice versa.
Sometimes, though, the concentration and distribution of melanin isn’t uniform, which leads to a condition known as heterochromia. This condition can present itself in different ways. There’s complete heterochromia, when each eye is a distinctly different color, say, one blue and one brown. Central heterochromia is when the eyes show various colors, such as a blue iris with a golden-brown ring around the pupil. And sectoral heterochromia is when one iris has a splash of color that’s different from its overall hue, a trait that actress Kate Bosworth has.
Eye pigmentation abnormalities are not necessarily a sign of an underlying health condition. This is known as simple heterochromia, and is generally inherited from a parent.
Heterochromia, however, is a common feature of several inherited genetic disorders. For example, Waardenburg syndrome causes children to experience hearing loss, prematurely graying hair and varying degrees of heterochromia. Another inherited disorder that lists heterochromia as a symptom is neurofibromatosis, which affects the nervous system and causes tumors to form on nerve tissue. Tumor formation inside the eye can cause heterochromia.
Irregular iris coloring can also be caused by an injury to the eye, such as a punch leading to bleeding within the eye. An infection or mild inflammation that affects only one eye can cause it, as can the presence of a foreign object in the eye, because that can lead to inflammation . Heterochromia can also be caused by glaucoma, which is a group of eye conditions that damage the nerve that carries visual information from the eye to the brain.
The sudden onset of heterochromia could be the sign of an underlying medical condition, and a complete eye exam should be conducted by an ophthalmologist to rule out any serious causes.
Original article on Live Science.
Remy Melina was a staff writer for Live Science from 2010 to 2012. She holds a bachelor’s degree in Communication from Hofstra University where she graduated with honors.
Why do some people have different-colored eyes
Why do some people have different-colored eyes
People with eyes of different colors are attracted to themselvesattention with its unusual appearance. In the Middle Ages, in times of superstition, a different color of the eyes was considered a sign of the witch and sorcerous abilities. However, the reason for this phenomenon is much simpler.
Sometimes you can meet people who have eyesdiffer among themselves in color. This phenomenon is called heterochromy and is very rare. Congenital heterochromia is a consequence of a mutation that occurs after the fertilization of the oocyte. In this case, it does not affect human health in any way. His vision and perception of colors is normal. It happens that the owner of the «multi-colored» eye is embarrassed because of its peculiarity. In this case, he can use colored lenses to make the eyes look the same. However, it is not recommended to constantly wear colored lenses, as opposed to conventional ones.
Complete and partial heterochromy
The word «heterochromia» comes from two Greekwords that are translated as «different» and «color». It can be genetic and acquired, complete and partial. Complete heterochromy is characterized by a complete difference in the colors of the iris of the eyes. The most common case is when one eye is blue and the other is of any other eye. Less common is partial, sector heterochromia, when different parts of the iris have a different color. For example, the iris is blue or green with brown patches. Partial heterochromy has no more than four people out of a million. There is also central heterochromy — when the area around the pupil has one color, and the iris — the other.
Acquired and genetically determined heterochromia
Genetically determined heterochromia usuallyinherited by the dominant feature. When heterochromia is transmitted genetically, it is usually manifested in the child only one month after birth, and initially the newborn has the same color. Traumas, tumors, inflammations, certain eye drops can be the cause of acquired heterochromia. If the discoloration of the eyes is a consequence of the disease, then after the cure, the former color is usually not returned. If a person suddenly starts to change the color of one or both eyes, it makes sense to go to the ophthalmologist for a checkup. The fact that different eyes color can talk about health problems. Iris darkening can occur with its chronic inflammation, melanoma, siderosis, hemosiderosis; and clarification — with Duane syndrome, acquired Horner’s syndrome, lymphoma, leukemia, heterochromic iridocyclitis Fuchs. Partial heterochromia can sometimes be a consequence of hereditary diseases, such as the Waardenburg Syndrome or Hirschsprung’s Disease.
The instance of a person having two differently colored eyes is pretty uncommon, just 11 out of every 1,000 Americans. This uncanny trait is caused by several factors, and can actually develop over time.
Iris color develops during the first few months after birth, with the levels of the pigment melanin determining how dark eyes will become. The less melanin expressed in the iris, the lighter a person’s eyes look, and vice versa.
Sometimes, though, the concentration and distribution of melanin isn’t uniform, which leads to a condition known as heterochromia. This condition can present itself in different ways. There’s complete heterochromia, when each eye is a distinctly different color, say, one blue and one brown. Central heterochromia is when the eyes show various colors, such as a blue iris with a golden-brown ring around the pupil. And sectoral heterochromia is when one iris has a splash of color that’s different from its overall hue, a trait that actress Kate Bosworth has.
Eye pigmentation abnormalities are not necessarily a sign of an underlying health condition. This is known as simple heterochromia, and is generally inherited from a parent.
Heterochromia, however, is a common feature of several inherited genetic disorders. For example, Waardenburg syndrome causes children to experience hearing loss, prematurely graying hair and varying degrees of heterochromia. Another inherited disorder that lists heterochromia as a symptom is neurofibromatosis, which affects the nervous system and causes tumors to form on nerve tissue. Tumor formation inside the eye can cause heterochromia.
Irregular iris coloring can also be caused by an injury to the eye, such as a punch leading to bleeding within the eye. An infection or mild inflammation that affects only one eye can cause it, as can the presence of a foreign object in the eye, because that can lead to inflammation . Heterochromia can also be caused by glaucoma, which is a group of eye conditions that damage the nerve that carries visual information from the eye to the brain.
The sudden onset of heterochromia could be the sign of an underlying medical condition, and a complete eye exam should be conducted by an ophthalmologist to rule out any serious causes.
Original article on Live Science.
Remy Melina was a staff writer for Live Science from 2010 to 2012. She holds a bachelor’s degree in Communication from Hofstra University where she graduated with honors.
I heard that there are some people have two different colored eyes. It is so strange. Why this happen?
Answers (3)
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coppercoconut19
01/23/2013
Yes it is a fact that some people have two different colored eyes. People’s eye color a manifestation of the pigment that is present in the iris. Two different-colored eyes within a single individual is comparatively very few in humans which is mainly caused by increased or decreased pigmentation of the iris. Although previously believed to be inherited in simple Mendelian fashion, eye color has proved to be a polygenic trait. And we hold that people may have two different colored eyes due to an alteration in the expression of the genes within the cells of the entire iris or even a particular section. It sounds quite interesting that people have two different colored eyes but it really exists and there is still a lot of fun to explore other possible underlying causes of it.
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The different colors of human’s eyes are related to the heredity and races. Different races have different colors of eyes. Eastern people and Western people have different chromocytes of iris. The hybrid people have different genes origination. So sometimes they may have two different colored eyes, it is normal and interesting. Theirs father and mother give them one eye gene superlatively. The chief actor of Prison Break of Michael Scofield who played by wentworth miller, he has two different colored eyes too. The left one is hazel and the right one is light green. He always wearing colored contact lenses to hide his secret, so it is hard to find this point from is photos.
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one reason is that some times pigments in your eye can mix up and change the eye colur
Jumpto
Recommend eye doctor & optical:
Melanin is a name for a group of pigments found in most organisms, including us, humans! Melanin is what makes our skin and hair appear darker or take a specific shade. We also have melanin in our eyes, but we will get to it soon. Melanin group includes several pigments, each «responsible» for their color. Those that impact our external appearance the most are brown eumelanin, black eumelanin, and yellow and red pigment pheomelanin. Eumelanin is both the most common and the most abundant, and typically is the one «missing» in cases of albinism. You have seen the effects of the changes in melanin in human bodies many times! For example, eumelanin in the reason we get gray hair with aging. Our hair itself is more or less transparent, and it is melanins that give it color. As the body ages, it stops producing brown eumelanin but continues producing the black eumelanin; hence the hair turns grey. At an even later age, even black one can fade away, leaving hair with no color (it appears white because of the optical effects). In human skin, the most readily observable change is tan: skin darkening after a day in the sun. Scientifically speaking, melanogenesis triggered by exposure to UV radiation. The UV radiation can be harmful, so it is a protective reaction of our skin. Melanin absorbs light very effectively and can dissipate the majority of the UV radiation. This is also the reason why people in sunny countries usually have darker skin, and people with very light, almost white skin get bad sunburns: they have less melanin to protect them. Pheomelanin gives skin more pink, red, or orange undertones. It is concentrated in nipples and lips, and some other body parts that appear redder than others. Pheomelanin makes your lip color different from the general tone of your face — red pheomelanin mixed with some brown eumelanin results in orange hair shade. The «redheads» with ginger or red hair often have slightly more pinkish skin tone, thanks to the pheomelanin. The same yellow, brown, and black pigments are present in our eyes, mainly in the iris and choroid. But there is no blue or green pigment at all! Neither in your eyes nor anywhere else. Your veins on the inside of your arm might appear greenish, blue, or violet: but in reality, they are not; they only look that way because of the overlay of the yellow-ish or pinkish skin over them. Here is the question: how come some people have those beautiful sky-blue or grass-green eyes if there is no green or blue pigment? Let’s find out. Your iris is a thin, circular structure in the eye with the pupil in its center. It overlays the lens and is responsible for the size of the opening (pupil), determining how much light penetrates it to the lens. If you have a professional camera, you can imagine it this way: the iris plays the role of the diaphragm, where the pupil is the «aperture.» The ocular lens is transparent, so, same as our skin, our eyes need it for protection from UV and other high-frequency light. This is why iris needs its pigments. The pigmented areas of the iris consist of several layers: the front fibrovascular layer known as stroma (contains pigmented elements of brown or yellow color) and, beneath the stroma, pigmented epithelial cells (mainly black). Iris’ shade is a very complex phenomenon: each visible, percieved color is a result of the combined effects of pigmentation, texture, and interlacing of the tissues and blood vessels within the iris. Pigmentation is still the most impactful factor, so if there is a lot of melanin in the eye, they would appear dark-colored. If there are no pigments at all, the iris would appear pink (the color of the blood vessels) or purplish (blood vessels plus some light scattering). In the eyes with little melanin in the stroma, various optical phenomena produce shades of blue and green. Those processes are very complex: selective absorption and reflection by biological molecules, Rayleigh scattering, Tyndall scattering, and diffraction — to name a few. Eyes with light yellow or amber color happen when the pigmented stromal cells contain pheomelanin with little eumelanin. If you only see yellow on the strong pupil contraction (when you stare at the bright light), it might be just the color of the contracting fibers. 
What Is Melanin?
How Melanin Determines Our Appearance
The «Missing» Blue And Green Pigment
What Is An Iris?
Melanin + Optical Physics = Eye Color