Where is pigment normally present in the iris

Eyes come in many shades, ranging from dark to light brown, and from green, hazel, and gray, to blue. But despite the many variations that we perceive, there are actually only two different pigments in our eyes: brown and red. The colored area at the front of the eye is called the iris. It is around 12 millimeters in diameter and has an opening in the middle, which is called the pupil. The iris is made from connective tissue and a thin muscle that allows it to open and close in response to light.

Our individual eye color is made up of different amounts of pigment and the connective tissue that forms part of the iris. The cells in the iris that make pigment are called melanocytes, and they are also responsible for the color of our hair and our skin.

Melanocytes can make two different types of pigment: eumelanin, which is brown-black, and pheomelanin, which is red. Dark eyes have the most pigment, particularly brown-black eumelanin.

In contrast, light blue eyes have the least amount of pigment. Light eye color is most prevalent in individuals of European descent. However, there is no such thing as blue pigment in our eyes.

A A A Type size. Commercial Moorfields Private Moorfields Dubai. Other Sites Biomedical Research Centre. Posterior chamber: The posterior chamber is between the iris and lens.

The lens is behind the iris and is normally clear. Light passes through the pupil to the lens. The lens is held in place by small tissue strands or fibers zonules extending from the inner wall of the eye. The lens is very elastic. Small muscles attached to the lens can change its shape, allowing the eye to focus on objects at varying distances. Tightening contraction or relaxing these muscles causes the lens to change shape, allowing the eyes to focus on near or far objects accommodation.

Vitreous chamber: The vitreous chamber is between the lens and the back of the eye. The back two-thirds of the inner wall of the vitreous chamber is lined with a special layer of cells the retina : millions of highly sensitive nerve cells that convert light into nerve impulses.

Nerve fibers in the retina merge to form the optic nerve , which leads to the brain. Nerve impulses are carried through the optic nerve to the brain. The macula, near the center of the retina at the back of the eyeball, provides the sharp, detailed, central vision for focusing on what is in front of you. The rest of the retina provides side peripheral vision, which allows you to see shapes but not fine details. Epub Jul 8.

White D, Rabago-Smith M. Genotype-phenotype associations and human eye color. J Hum Genet. Epub Oct Other chapters in Help Me Understand Genetics. Genetics Home Reference has merged with MedlinePlus. Learn more.

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health. Is eye color determined by genetics? From Genetics Home Reference. Topics in the Genetics and Human Traits chapter Are fingerprints determined by genetics? Is intelligence determined by genetics?