Central Heterochromia vs. Hazel Eyes: What Is the Distinction?
December 2, 2024 • 5:52 PM
The human eye is delicate and complex, and its colors can vary in incredible ways. Sometimes, the pigmentation in a person’s eyes takes on a unique form called central heterochromia. It’s not a common condition and is generally harmless, but it’s still worth learning about.
Central heterochromia can look deceptively similar to the classic hazel eye color, but the two differ in several key ways. Let’s look at the basics of central heterochromia and how it differs from hazel eyes in this guide from Pair.
What Is Central Heterochromia?
Central heterochromia is an eye trait that causes your iris to take on two different colors. These colors coexist in distinct concentric rings, with one inner ring nearer to the pupil and an outer ring with a different hue.
The telltale signs of central heterochromia are:
- Two different color zones coexist within the iris and do not blend. In contrast, folks with hazel eyes may appear to have multiple hues that blend together in their pupils.
- There is symmetry between both eyes, rather than one eye looking different than the other. For example, a person with central heterochromia might have partially blue eyes and partially amber eyes, with the same color gradient on both the left and right.
- Most people with central heterochromia don’t have any reason to believe their eye color is associated with an underlying condition. In general, central heterochromia is benign and simply results from differences in melanin concentration in the iris.
What Causes Central Heterochromia?
In most cases, central heterochromia is an inherited trait. It occurs when deposits of melanin in a person’s irises aren’t distributed evenly, creating unique layers of color.
While this trait is usually benign, it can be caused by medical conditions like Horner’s syndrome, which we’ll discuss later on.
What Are Hazel Eyes?
Hazel is a unique eye color with green, dark brown, and golden hues. While people with central heterochromia may have these colors in their irises, folks with hazel eyes have a balanced gradient of different eye colors rather than what you see in various types of heterochromia.
Key traits of hazel eyes include:
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A natural mixing of different pigments that don’t have any defined zones.
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The appearance of color changes based on light and other factors. For example, people with hazel eyes sometimes appear to have green eyes or brown eyes based on the lighting in a room, the clothes they wear, or even eye makeup.
- Most people with hazel eyes generally have a distinct color that dominates the mix. This color is usually light or medium brown, with flecks of green and gold. A person who has primarily green eyes with brown flecks might be described as having “hazel-green eyes.”
What Causes People To Have Hazel Eyes?
The amount of melanin and lipochrome in a person’s irises causes hazel eyes. These sources of pigmentation create a distinct color blend, and they’re also responsible for how hazel eyes seem to change in response to light.
What Are the Difference Between Central Heterochromia and Hazel Eyes?
There are a few key differences that set central heterochromia apart from hazel eyes:
Blending
A person with hazel eyes has a seamless blend of different colors orbiting their pupils. On the other hand, a person with central heterochromia has two distinct zones of color around their pupils.
Uniformity
Hazel eyes sometimes vary in coloring between the left and right, and their coloring can shift in response to light. However, central heterochromia makes a person’s eye color look uniform and symmetrical.
Color
Hazel eyes usually have a light brown or amber base color, with bits of green or gold throughout. On the other hand, a person with central heterochromia may have primarily blue or gray eyes.
Causes
In cases of central heterochromia, a person has less melanin in some areas of their irises, partially changing the iris color. For hazel eyes, melanin, lipochrome, and changes in light scattering are the main reasons behind the colors you see.
Why Do People Have Different Eye Colors?
Eye color is shaped by genetics. Variations in the OCA2 and HERC2 genes are why you might have a different eye color than another family member. That’s because these genes regulate melanin production in your irises.
In addition to genetic mutations, the Tyndall effect also affects your eye color. This phenomenon refers to how light is scattered in the stroma, the front layer of your iris. It’s why people with hazel eyes seem to change hues in different environments.
Is Central Heterochromia a Cause for Concern?
Thankfully, central heterochromia is rarely an issue —it’s just a part of a person’s unique look. This trait is caused by uneven pigmentation in the eyes, which isn’t directly linked to eye health problems.
However, if central heterochromia develops suddenly, it might be linked to one of these conditions:
Horner’s Syndrome
Horner’s syndrome is a rare condition that interrupts nerve signals from the brain to the eye and one side of the face. This condition can cause sudden changes to your eyes, sometimes affecting pigmentation.
However, the major distinction between Horner’s syndrome and central heterochromia is the other symptoms. Horner’s often causes a drooping upper eyelid (known as ptosis) and constriction in the pupil of one eye. Additionally, only one side of the face is affected, while central heterochromia almost always affects both eyes.
Horner’s syndrome is often caused by nerve damage, which can develop because of a stroke or spinal cord injury. In general, Horner's has much more severe and rapid-onset symptoms that will indicate that medical attention is needed. Changes in a person’s iris coloration won’t be the telltale sign.
Fuchs’ Heterochromic Iridocyclitis
This rare, chronic eye condition causes inflammation in the middle layer of the eye. It’s characterized by a difference in color between the eyes, distinguishing it from typical cases of central heterochromia.
People with FHI are often more prone to conditions like cataracts and glaucoma, which makes it worthwhile to visit an eye doctor or ophthalmologist for an eye exam. If you’re unsure whether you’re dealing with FHI or central heterochromia, your eye doctor can help you get an accurate diagnosis and treatment plan.
Pigment Dispersion Syndrome
Pigment dispersion syndrome is a type of glaucoma that can sometimes look similar to central heterochromia. The most significant difference is that the pigmentation changes happen suddenly, forming tiny pigment granules in the anterior part of the iris.
Like other forms of glaucoma, pigment dispersion syndrome always needs treatment from an ophthalmologist. Without care, glaucoma can lead to vision loss and other serious problems.
How To Own Your Eye Color
Whether you have central heterochromia or classic hazel eyes, confidence is key. Once you’ve determined that your eye pigmentation isn’t a sign of an underlying condition, you’re free to focus on owning your eye color and making it a part of your look.
One of the best ways to feel great about your eye color is to complement your hue with a pair of stylish glasses. Pair makes it easy to do just that with our wide selection of Base Frames and unique, magnetic Top Frames.
In our online store, you can find a pair of Top Frames that accentuate the natural colors of your eyes and complete your look. Plus, you can easily swap out your frames whenever your mood changes.
Unique Glasses for Unique Eyes
Central heterochromia and hazel eyes are two distinct variations of eye color that look absolutely amazing in their own right. They might look similar at first, but these two colorings are very different — and worth celebrating.
For prescription glasses, blue light glasses, or sunglasses to complement even the rarest eye color, Pair has you covered.
Sources:
Horner Syndrome: What It Is, Causes, Symptoms & Treatment | Cleveland Clinic
What Is Pigment Dispersion Syndrome? | American Academy of Ophthalmology
Colored Rings in the Iris | American Academy of Ophthalmology