When we talk of the color of a person's eyes, we are referring to the color of the iris. The iris is the colored disk in the center of the eye. The color of the iris which can range from brown, black, blue, green, gray and hazel is caused by the amount of the pigment melanin that is present. Melanin is also the pigment that gives color to our skin and hair. Not many people know that the iris gets its name from the variety of colors that are possible. Iris is the Greek word for rainbow!
There are those who, because of genetic defects or chemical imbalances in the body, do not have enough melanin to give color to the skin or hair - these people, who are completely colorless, are known as Albinos. The lack of pigmentation in the iris results in pink eyes. In some cases, people can have eyes of two different colors. This is nothing to be concerned about and is the result of a small genetic quirk.
A common accepted fallacy is that the color of the iris changes as a child grows into adulthood. It does not. It may appear to be of a different hue, but that is usually caused by a reflection of the ambient colors or may be an illusion caused by the color of the clothes a person is wearing on a particular day.
The iris is made up of tissue and smooth muscle fibers. It is these tissues and muscles that cause the pupil, the dark spot located in the center of the iris, to expand and contract. Light enters the eye through the pupil and reaches the retina which interprets the light as images. An excess of light can hurt the retina. That is why when the light is overly bright, the muscles of the Iris cause the pupil to contract, thus allowing less light to enter the eyes. But when ambient light is low, the iris causes the pupil to open wide, allowing maximum light to enter the eye so as to allow for the maximum possible vision.
The movement of the iris muscles in opening and closing the pupil is not always fast enough to protect the eye which is why when faced with bright light, we squint and almost close our eyes, until the iris has caused the pupil to contract enough. Similarly when we enter a dark room, it takes us a few moments before we can recognize shapes and outlines. This is the time the iris needs to open the pupil fully.
An interesting result to the speed with which the iris responds to light is the photographic phenomenon known as "red eye." This occurs when a flash is used to take a photograph. People in this photo appear to have glowing red eyes. This is because of the bright flash light reflecting back from the rear of the eye and looking red.
The color, texture and patterns of each person's iris are completely unique - even more so than fingerprints. That is why one of the latest advancements in security are scanners and software that scans a person's iris to establish his or her identity. While fingerprint readers can be fooled, doing the same to an Iris scanner is almost impossible.
Although protected from direct contact with the external environment by the cornea, the iris is prone to infection. The most common of these is iritis which is an inflammation of the muscles of the iris. If the inflammation is allowed to persist for an extended period of time, the inflamed muscles can cause the shape of the pupil to become permanently changed. A misshapen pupil can lead to glaucoma and other vision defects.
Iritis is a serious condition. Any irritation of the iris should be referred to a medical specialist as soon as possible. With early detection and treatment the attack will soon fade away with the minimum of discomfort. But if the infection is allowed to fester over a period of time, the treatment will involve much stronger medication, with the resultant side effects. It will also take a much longer period of time. Untreated iritis has been know to lead to other complications and can even result in blindness.
Iritis may also be a symptom of some other disease such as TB, Lyme Disease, Syphilis, Herpes and cancers like Leukemia, Lymphoma and Melanoma.
This does not mean that every eye irritation or inflammation is a reason to panic. But it does emphasize the need to pay attention to the health of the eyes and not take them for granted.
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