Iris

Overview

What is the iris of the eye?

The iris is the colored part of your eye. Muscles in your iris control your pupil — the small black opening that lets light into your eye.

The color of your iris is like your fingerprint. It’s unique to you, and nobody else in the world has the exact same colored eye.

Function

What does the iris of the eye do?

Muscles in your iris control your pupil. When your pupil is wider (dilated), more light gets into your eye. When it’s narrower (contracted) less light gets in.

As your iris squeezes or releases your pupil the amount of light reaching the rest of your eye changes. This constant change in size helps you see in different lighting. You’ve experienced this if you’ve stepped outside on a bright day or come inside after some time in the sun. The time it takes your eyes to adjust to the light is your irises adjusting your pupil to help you see.

How does the iris help the eye function?

The iris controlling your pupil helps your eyes see clearly. The iris is constantly changing how dilated your pupil is without you controlling it. This is called the pupillary light reflex.

Some people are born without an iris in one or both of their eyes — a genetic condition called aniridia. Without an iris, your eye would still function, but your vision would be blurry.

Anatomy

Where is the iris in the eye?

The iris surrounds the pupil at the center of your eye.

Your eyeball has several layers that sit on top of each other, like an onion. The iris is one layer from the outside — under the cornea on top of the lens.

What does it look like?

The iris is the part of your eye that’s colored. It’s flat and round.

Your eye color depends on how much melanin (a naturally occurring pigment) your body makes and certain genes. The genes that determine your eye color are passed down through your parents.

What is the iris made of?

The iris is made of muscles and nerves. The nerves and muscles in your iris work on their own without you thinking about them (parasympathetically) to control the size of your pupil.

Your iris is filled with a fluid called aqueous humor. Your eye constantly produces and drains aqueous humor to maintain its shape, size and pressure.

Conditions and Disorders

What are the common conditions and disorders that affect the iris?

The iris can be affected by any condition that affects your eyes, including:

Your iris can also be damaged during trauma or injury. Surgery on your eyes and some medications can affect your iris too.

Can iris scanners damage your eyes?

Scanners that use your face and eyes are increasingly common ways to unlock phones, computers and other security devices. These scanners bounce a small amount of infrared light off your face and eyes to verify your identity. There’s no evidence these devices are dangerous or can harm your eyes.

What are signs or symptoms of problems with my iris?

Talk to your healthcare provider if you notice any symptoms in your eyes, including:

  • Blurry vision.
  • Double vision (diplopia).
  • New pain that doesn’t go away in a few days.
  • Light sensitivity.
  • Your vision is getting noticeably worse.

What tests are done to the iris?

Your provider will check your irises as part of your overall eye exam. If they’re checking your eyes for a specific condition or issue, you might need imaging tests, including:

Care

How do I take care of my iris?

Wear sunglasses with 100% UV protection or a UV400 label anytime you’re in the sun.

Tell your healthcare provider about any changes in your vision. If you wear glasses or contact lenses, have your eyes examined regularly so your provider can adjust your prescription as often as necessary.

When should I see my healthcare provider?

See your healthcare provider as soon as you notice any changes in your vision. Whether it’s something as simple as needing new glasses, or a more serious condition, don’t wait for symptoms to get worse before having your eyes checked.

Go to the emergency room if you suddenly lose your vision or have severe pain in your eyes.

A note from Cleveland Clinic

The iris is like a colored fingerprint that’s unique to you. But it’s not all about your one-of-a-kind eye color. Your irises play an important role in your ability to see clearly in every situation. Get regular eye exams as part of your overall health maintenance, and talk to your provider as soon as you notice any changes in your vision.

Last reviewed by a Cleveland Clinic medical professional on 02/20/2022.

References

  • American Academy of Ophthalmology. Eye Anatomy: Parts of the Eye and How We See. (https://www.aao.org/eye-health/anatomy/parts-of-eye) Accessed 1/20/2022.
  • International Commission on Non-Ionizing Radiation Protection. ICNIRP Guidelines on Limits of Exposure to Incoherent Visible and Infrared Radiation. (https://journals.lww.com/health-physics/Abstract/2013/07000/ICNIRP_Guidelines_on_Limits_of_Exposure_to.9.aspx) Health Physics. 2013 Jul 105;1(74-96). Accessed 1/20/2022.
  • MedlinePlus. Aniridia. (https://medlineplus.gov/genetics/condition/aniridia/#causes) Accessed 1/20/2022.
  • MedlinePlus. Iris. (https://medlineplus.gov/ency/article/002386.htm) Accessed 1/20/2022.
  • StatPearls. Anatomy, Head and Neck, Eye Iris Sphincter Muscle. (https://www.statpearls.com/ArticleLibrary/viewarticle/23763) Accessed 1/20/2022.

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy