Eye Makeup
Classification of colors
The perception of color depends upon various factors. These are the same eyes; however, depending on the light and surrounding hues, the eye color can appear quite different.
Iris color can provide a large amount of information about an individual and a classification of various colors may be useful in documenting pathological changes or determining how a person may respond to various ocular pharmaceuticals.Various classification systems have ranged from a basic "light" or "dark" description to detailed gradings employing photographic standards for comparison.Others have attempted to set objective standards of color comparison.
As the perception of color is dependent on viewing conditions (e.g. the amount and type of illumination, as well as the hue of the surrounding environment), so is the perception of eye color.
Eye color exists on a continuum from the darkest shades of brown to the lightest shades of blue.Seeing the need for a standardized classification system that was simple, yet detailed enough for research purposes, Seddon et. al developed a graded one based on the predominant iris color and the amount of brown or yellow pigment present. There are 3 true colors in the eyes that determine the outward appearance; brown, yellow, and blue. How much of each color you have determines the appearance of the eye color. The color of the eyes in turn depends on how much of these colors are present. For example, green eyes have yellow and some blue, making them appear green. Blue eyes have a little yellow and little to no brown, making them appear blue. Gray eyes appear gray because they have a little yellow and no brown in them. Brown eyes appear brown because most of the eye contains the brown color. The above is true for the species Homo sapiens. The iris color can vary in the animal world. Instead of blue in humans, autosomal recessive color in the species Corucia zebrata is black, whereas the autosomal dominant color is yellow - green.
Brown
In humans, brown eyes contain large amounts of melanin (eumelanin) within the iris stroma which serves to absorb light, particularly at the shorter wavelengths. If eye color were to be listed from most common to least common, brown eyes are most common. Very dark brown irises may appear to be black.
Dark brown human iris
Brown is predominant and, in many populations, it is (with few exceptions) the only iris color present. It is least common in the countries around the Baltic Sea, mostly in Finland and Estonia.
Hazel
Some eye colors are too mixed to identify properly, and are misidentified as hazel for simplicity's sake.
Hazel eyes are due to a combination of a Rayleigh scattering and a moderate amount of melanin in the iris' anterior border layer.A number of studies using three-point scales have assigned "hazel" to be the medium-color between light brown and dark green. This can sometimes produce a multicolored iris, i.e., an eye that is light brown near the pupil and charcoal or amber/dark green on the outer part of the iris (and vice versa) when it is open to the elements of the sun/shined in the sunlight. Hazel is mostly found in some regions of the Americas and Europe. Rarely, hazel eyes can be found in people with African, Middle Eastern and Asian descent.
This eye shows the shift in color from brown to gold to green.
There is some difficulty in defining the eye color "hazel" as it is sometimes considered to be synonymous with light-brown, gold, and other times with dark green.Hazel eyes have been described as dark green or yellowish brown, or as a lighter shade of brown. Hazel eyes have also been described as being equivalent to a dark green or amber color eyes/light brown. In North America, "hazel" is often used to describe eyes that appear to change color, ranging from light brown to green and even gray, depending on current lighting in the environment.
Amber
Human amber eyes displaying the yellow pigments.
Amber eyes are of a solid color and have a strong yellowish/golden and russet/coppery tint. This might be due to the deposition of the yellow pigment called "lipochrome" in the iris (which is also found in green and violet eyes). They are nicknamed "Wolf eyes" due to the high rate of the amber eye color in wolves.
An amber eye
The eyes of some pigeons contain yellow fluorescing pigments known as pteridines. The bright yellow eyes of the Great Horned Owl are thought to be due to the presence of the pteridine pigment xanthopterin within certain chromatophores (called xanthophores) located in the iris stroma.In humans, yellowish specks or patches are thought to be due to the pigment lipofuscin, also known as lipochrome.
Green
A woman with green eyes
Green eyes
Green eyes are the product of moderate amounts of melanin. Only 1-2% of the world's population has green eyes. Green eyes are the least common eye color. They are most often found among people of Northern Europe, and to a lesser extent, in Southern Europe, parts of Central and South Asia.Other ethnically Nordic countries like Sweden, Denmark, Norway, and (less) the Netherlands have a high percentage of green eyes. The Pashtuns are often called "Hurry Ankehian Wallay": the green-eyed people.
Gray
Female gray eyes
Gray eyes have more melanin than blue eyes , and usually gray eyes are considered a darker shade of blue (like blue-green). They are most common in European Russia, Finland and the Baltic States. Gray eyes are connected to scant pigmentation overall: those who have gray eyes often have pale skin and light hair (blond, brown, and red).
Under magnification, gray eyes exhibit small amounts of yellow and brown color in the iris.
A steel blue-gray eye
Male gray eyes
A gray iris may indicate the presence of a uveitis. However, other visual signs make a uveitis obvious.
Visually, gray eyes often tend to appear to change between the shades of blue, green and gray. This is said to be influenced by the lighting and the surroundings (such as clothes, makeup, etc.).
The Greek goddess Athena was renowned for having "owl-gray" (in Greek, γλαυκῶπις – glaukōpis) or "sea-gray" eyes.
Blue
A blue eye
Blue eyes contain low amounts of melanin within the iris stroma; longer wavelengths of light tend to be absorbed by the underlying iris pigment epithelium, and shorter wavelengths are reflected and undergo Rayleigh scattering. The type of melanin present is eumelaninThe inheritance pattern followed by blue eyes is considered similar to that of a recessive trait, however it is a polygenic trait ( meaning that it is controlled by the interactions of several genes, not just one). Eiberg and colleagues showed in a study published in Human Genetics that a mutation in the 86th intron of the HERC2 gene, which is hypothesized to interact with the OCA2 gene promoter, reduced expression of OCA2 with subsequent reduction in melanin productionThe authors concluded that the mutation may have arisen in a single individual around the Black Sea region 6,000-10,000 years ago, except blue eyes with brown spots around the pupil who are not related to this mutation.
Blue eyes are mostly common throughout Northern and less in Eastern Europe.One survey estimated that nearly 90% of Icelanders have blue or green eyes. Blue eyes are common in Ireland, Germany, The British Isles, Netherlands , Austria, Poland and in Scandinavian countries. They are also present in Southern Europe and rarely in India and in some population of Central Asia and Middle East especially in lebanon. They are seen as a common trait among the Pashtun community in the North-West Frontier Province of Pakistan.
A 2002 study found the prevalence of blue eye color among Whites in the United States to be 33.8% for those born between 1936 and 1951 compared to 57.4% for those born between 1899 and 1905.
As melanin production generally increases during the first few years of life (especially if exposed to the sun), the blue eyes of some babies may darken as they get older.
Violet
The appearance of violet eyes is thought to occur from the mixing of red and blue reflectionsSome albinos have eyes that appear violet. The actress Elizabeth Taylor is famous for her violet eyes
Red
'Red' eyes are also found in an extremely small percentage of the world's population.[citatio needed] This is believed to be a result of either large quantities of the normally scarce red areas in the eye, or a small leakage of blood into the iris. Red eyes commonly appear in photos due to the Red-eye effect.
