The iris is the colorful part of the eye that regulates the size of the pupil based on light exposure. It’s made up of four layers and consists of muscles, nerves, and pigmented cells that contribute to eye color and overall eye function.
People often ask, “Can eyes change color?” In rare cases, a person’s eye color can change due to factors related to age, genetics, medical conditions, or eye trauma. Harmless causes include infant eye color changes, freckles, and taking certain medications. In contrast, more serious conditions like Fuchs heterochromic iridocyclitis, pigment dispersion syndrome, or eye injuries can also lead to changes in iris pigmentation.
Regular eye exams are essential for detecting any underlying health concerns related to iris color changes.
What Is the Iris?
The iris is the colorful part of the eye surrounding the pupil. It’s a unique structure in that its pattern and design are distinctive to every person, much like fingerprints. It’s so unique that some access control systems will scan a person’s iris for verification instead of relying on a keycard or access code.
While the iris is a defining feature of a person’s face, it also has a functional purpose—it controls the size of the pupil and regulates the amount of light that can enter the eye.
The iris consists, in part, of muscles that contract or relax to close up and open the pupil, depending on how much light a person is exposed to. When there is very little light, the iris will open the pupil up significantly to let as much light in as possible—this allows the person to see as much as they are able in dim or dark settings. When there is an abundance of light, the iris will close the pupil to where there is only a small opening. This protects the retina, macula, and other components of the inner eye from light-inflicted damage.
Where Inside the Eye Is the Iris?
The iris is positioned in the aqueous humor, the clear liquid in the front part of the eye that keeps everything nourished, inflated, and overall healthy. It also sits in between the cornea and the lens, two structures that protect the eyes and dictate visual acuity, or the ability to see objects clearly.
What Makes Up the Iris?
The iris is made up of muscles, nerves, connective tissues, and cells, including pigmented cells that give it its color.
Each iris has four layers. Starting from the front of the iris to the back, the layers include the anterior border layer, stroma, anterior epithelium, and posterior epithelium.
The Anterior Border Layer
The anterior border layer is the first layer of the iris that people can see and consists of a mix of fibers, cells, and melanocytes, or pigmented cells. This layer contributes to the iris’s texture, pattern, and color.
The Stroma
The stroma is a thick, complex layer of the iris that consists of cells and extracellular matrix, a non-cellular system of proteins, glycoproteins, proteoglycans, carbohydrates, and more. The stroma also contains blood vessels and nerves, and it plays a role in the pupil’s opening and closing. It’s also the layer that contains the most pigmented cells that dictate eye color.
The Anterior Epithelium
The anterior epithelium is the third layer of the iris that shares space with the dilator muscle, or the muscle that dilates (opens and closes) the pupil. It also has a few melanin granules that contribute to the overall eye color.
The Posterior Epithelium
The posterior epithelium is the final layer of the iris. It comes in direct contact with the posterior chamber, a small cavity between the iris and the lens. The posterior epithelium is a tight formation of cells and other structures that protect the inner eye from light exposure.
Can the Color of the Iris Change Over Time?
The short answer is, “Yes, the eyes can change color!” But it’s rare and, in most cases, minor.
Natural changes, genetics, Autoimmune disease, eye trauma, and other conditions or events can cause the iris to change color. A changing iris could be caused by something harmless, or it could indicate a more serious threat to the patient’s health.
Harmless Causes
Eye Color Changes in Infancy
Eye color change is most noticeable in infancy, as babies with little to no pigment in the iris will be born with light blue or gray eyes. Usually, by the time they reach 6 months of age, their eyes will have produced more melanin pigment, and the color will change to green, hazel, or brown.
Eye Freckles
People can develop freckles, or small brown spots, on their irises, usually as a result of too much sun exposure. These freckles are harmless to the eyes, just as they are harmless to the skin.
Eye Nevi
Nevi are larger freckles on the iris that can look mole-like. Uncommon and usually harmless, nevi can be a risk for cancer. Your eye doctor should monitor any nevi that may develop.
Arcus Senilis
It’s common for older people to develop a white ring on their cornea, which is really a buildup of lipids. This ring can affect the appearance of the eye color.
Glaucoma Medication
Many glaucoma patients must take medications called prostaglandins to help manage their condition. Sometimes, the effects that glaucoma medication can have include harmless but permanent darkening of the eye’s natural color.
Troublesome Causes
Fuchs Heterochromic Iridocyclitis
Fuchs heterochromic iridocyclitis is an inflammation of the front layers of the eyes, including the iris. As a result of the inflammation, the iris can lose pigmentation. It can also lead to the development of glaucoma or cataracts.
Iridocorneal Endothelial (ICE) Syndrome
ICE syndrome is a rare and dangerous development that causes the cells in the cornea to move to the iris, leading to the development of spots on the iris. ICE syndrome typically affects one eye and is a warning sign of glaucoma.
Pigment Dispersion Syndrome
Pigment dispersion, or pigment loss, is a condition in which the pigment cells in the back of the iris break away and move to other parts of the eyes. Not only can this change a person’s eye color, but these cells can also clog the eye’s drainage system, cause pressure buildup in the eye, and lead to the development of glaucoma.
Eye Injury
Trauma to the eye can result in tissue loss in the iris, which could lead to a permanent change in the iris’s color.
Have you noticed your iris changing color recently? Schedule an appointment with Vision Eye Group today for a thorough evaluation of your iris’s health.
The ophthalmologists and optometrists at Vision Eye Group can evaluate your eyes and check for any dangerous underlying conditions that may be causing them to change color. We offer thorough diagnosis, treatment, or management for any eye conditions you may be developing.
Schedule an eye exam with Vision Eye Group today: 478-744-1710
Vision Eye Group serves patients throughout Middle Georgia with offices in Macon, GA, and Warner Robins, GA.
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