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What Is the Iris of the Eye Made Of?

The iris is the colored portion of the eye that is as different from person to person as fingerprints.

  1. Location

    • The iris separates the cornea from the lens. It divides the anterior compartment into two parts: the anterior chamber and the posterior chamber.

    Layers

    • Three layers make up the iris. From front to back, these layers are called the endothelium, stroma and epithelium.

    Color

    • Pigment makes the eyes look blue, green, hazel or brown. An albino has no pigment and the iris looks pink.

    Genetics

    • Genetics control the type of pigment in an iris. People predisposed to brown eyes have more melanin pigment, caused by a gene on chromosome 15. Blue eyes are the result of lipochrome, which is caused by a gene on chromosome 19.

    Muscles

    • Muscles in the iris control the opening and closing of the pupil. In dim light, the dilator muscles in the iris cause the sphincter muscle around the pupil to dilate in order to let in more light. Alternatively, these muscles contract the pupil in bright light.

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