Why do irises have different colors

Before then, everyone had brown eyes. Blue eyes have probably spread through the population just because some people like how they look and chose to have children with blue-eyed people. Green and hazel eyes are a mixture of pigment color and color from scattered light, so they can also look different in different lighting conditions.

Babies often do not have much pigment in their irises when they are born. This is why their eyes can look very blue. For most children , eye color stops changing after the first year, but for some kids the color can continue to change for several more years. The Academy surveyed more than 2, Americans to determine what color eyes they have.

Below are the results of that Harris Poll survey, weighted to reflect the United States population at that time. About Foundation Museum of the Eye. Eye Facts and Science. Los ojos azules no son realmente azules. By Dan T. Hint: Eye color depends on the iris The colored part of the eye is called the iris. Heterochromia that develops later in life due to illness, injury, or medication, is known as acquired heterochromia.

This is less common than the genetic form. In addition, a medication called latanoprost, which is used to treat glaucoma, has been associated with changes in eye color in up to 33 percent of those taking it for 5 years or longer. Latisse, which is a drug once used to treat glaucoma but now primarily used to thicken eyelashes, may also account for a change in eye color. Central heterochromia is characterized by having two different colors in the same iris.

Usually, the outer ring of the iris is one color while the inner ring is another. People with this condition have two different-colored eyes. For example, they may have one blue eye and one brown eye. In people with sectoral heterochromia, also known as partial heterochromia, one part of the iris is a different color from the rest.

Sectoral heterochromia often resembles an irregular spot on the iris of the eye and does not form a ring around the pupil. Heterochromia of the eye is easy to identify. The person will have two different colored eyes or color differences within one or both eyes. Color differences may be slight and may only become apparent under certain lighting conditions or in photographs.

Aside from variations in eye color, there are usually no other signs and symptoms of heterochromia. However, if a medical condition or trauma is responsible for the heterochromia, other signs and symptoms may be present.

Most cases of central heterochromia are benign. They are not linked to medical conditions and do not affect vision or lead to complications. However, a checkup is necessary to rule out other medical conditions. People who acquire heterochromia and people whose genetic heterochromia changes in appearance should see an eye doctor.

An eye examination will usually be necessary, and other tests, including blood tests and chromosome studies, may be needed. According to the American Academy of Ophthalmology , if no other issues are present, treatment is not usually necessary. Because the iris is a key component in filtering out the light that enters our eyes, it makes sense that the iris would need protection. In humans and animals, that protection comes in the form of melanin.

Melanin is derived from a form of amino acids called tyrosine. Typically ranging from black to brown, the pigments in melanin absorb light to filter it away from more sensitive parts of the body. Melanin is found all over the body, including hair, the eye, skin, and even parts of the inner ear and brain!

The easiest way to see melanin in action is to spend some time in the sun. But then, genetic mutations began to affect certain genes and reduced the amount of brown pigments being produced in the front of the iris. For colors such as green, gray, or olive, these are halfway colors that are caused by more pigment than blue eyes, but less than brown.

These days, there are so many colors of eyes to behold, that scientists have added several gradients to their color scale beyond blue, green, or brown. Here are a few of the most rare and interesting. People with albinism have been born with a congenital disorder related to pigment production in their bodies.

Albinism may cause a person to have either partial loss of pigment or complete loss. This deficiency carries over to the eyes. Because there is no pigment to cause the iris to appear opaque, you are able to see the red of the retina.