Definition

The iris is a donut-shaped membrane around the pupil, which adjusts the amount of light entering the eyeball by controlling the size of the pupil through contraction and relaxation.

Location

It is located inside the eyeball, between the cornea and the lens.

Structure

The hole located in the center of the iris is called the pupil, and the iris plays the role of an aperture that adjusts the amount of light entering the eye. The iris is adjusted by the pupil constrictor muscle and the pupil dilator muscle located inside the iris, causing the pupil to enlarge and shrink. The color of the iris appears in various ways due to the pigment layer inside the iris. There are many differences by race and individual, there can be differencㄷes between both eyes, and even in one eye, the color and shape can appear differently. If the iris has a small amount of pigment, it becomes blue or gray, and if it has a lot of pigment, it appears brown. In the case of Westerners, because the amount of pigment is small, when exposed to sunlight, it passes through the iris as it is, so it is more dazzling compared to Easterners.

Function

In a place with a lot of light, the iris dilates, making the pupil smaller, thus reducing the amount of light entering the eyeball. In a place with less light, the iris contracts, making the pupil larger, thus increasing the amount of light entering the eyeball.

Health Tip

Heterochromia iridis
Different colors in both eyes is called heterochromia, and it is also referred to as Odd-eye. This occurs due to the different amounts of pigment in the iris, which is the part around the pupil, and it originates from hyperpigmentation and hypopigmentation of the iris. In the congenital genetic disorder known as Waardenburg syndrome, heterochromia is a characteristic feature, typically with one eye being brown and the other blue. It can also occur as a result of trauma or during the treatment process for glaucoma due to medication.

Inflammation occurring in the iris can be caused by infection, but it can also appear in conjunction with non-infectious diseases such as ankylosing spondylitis, Behcet’s disease, juvenile rheumatoid arthritis, and psoriasis. Iritis, which appears in these diseases, is one of the important aspects in diagnosing the disease.