Multicolored eyes, also known as heterochromia, are quite rare. Only around 1% of the global population has two different colored eyes. While it is not common, it is a unique trait that some people are born with. Keep reading to learn more about the causes, types, rarity, and interesting facts about multicolored eyes.
What is heterochromia?
Heterochromia refers to a difference in coloration in the iris, the colored part of the eye. It can be complete or sectoral. Complete heterochromia is when one iris is a different color than the other. Sectoral heterochromia is when part of one iris is a different color from its remainder.
For example, someone with complete heterochromia may have one blue eye and one brown eye. Someone with sectoral heterochromia may have a brown iris with a slice of blue in part of it.
What causes heterochromia?
There are a few potential causes of heterochromia:
– Genetics – Heterochromia can be passed down genetically. The gene responsible for eye color is inherited as a dominant trait, meaning only one parent needs to pass down the gene for a child to inherit it.
– Congenital – Some babies are born with heterochromia with no family history. In these cases, it occurs due to a random genetic mutation during fetal development.
– Injury or Disease – Trauma, certain medications, and some illnesses can cause a change in iris color later in life. For example, some cancers, autoimmune disorders, or viral infections can lead to iris discoloration.
– Pigment Disorders – Conditions like Waardenburg syndrome disrupt melanin production, causing different amounts of pigment in each eye. Horner’s syndrome can cause one iris to become paler.
Types of heterochromia
There are a few different types of heterochromia defined by appearance:
– **Complete heterochromia** – Each eye is a distinctly different color. This is the least common type.
– **Sectoral heterochromia** – Part of one iris is a different color from the rest. This is the most common heterochromia in humans.
– **Central heterochromia** – There is a ring around the pupil of a different color than the rest of the iris.
– **Mixed or complicated heterochromia** – There is more than one variation of color in a single iris. For example, a brown iris with a green sector and a central ring of blue.
| Type | Description |
|---|---|
| Complete heterochromia | One eye a different color than the other |
| Sectoral heterochromia | Part of one iris a different color |
| Central heterochromia | Ring around pupil a different color |
| Mixed/complicated heterochromia | Multiple color variations in one iris |
Common eye color combinations
While any colors can occur, some eye color pairings are more common than others:
– One blue eye, one brown eye – This is the most common form of complete heterochromia. Brown eyes contain a lot of melanin, while blue eyes contain very little. Having one parent with brown eyes and one with blue can result in this combination.
– Blue-green eyes – Green eyes have low to moderate amounts of melanin. Having a mix of melanin in one eye can produce a striking blue-green hue.
– Blue-gray eyes – Low melanin levels result in blue while moderate levels appear gray. Together this can create a pale icy blue-gray iris.
– Brown-amber eyes – Amber eyes are a golden yellowish-brown resulting from higher melanin levels. Paired with a darker brown eye, this is a relatively common sectoral heterochromia.
Is heterochromia associated with any health conditions?
Most of the time heterochromia is completely benign and does not affect vision or health in any way. However, in some cases it can be linked with certain underlying health conditions:
– **Waardenburg syndrome** – This genetic disorder affects skin, hair, and eye pigmentation. Multicolored eyes are one of the main symptoms. People with this syndrome should be evaluated for potential hearing loss which commonly accompanies it.
– **Horner’s syndrome** – This condition affects nerves in the eyes and can make one iris paler than the other. It is often caused by damage or disruption of sympathetic nerves.
– **Sturge-Weber syndrome** – A congenital disorder that can cause abnormalities in blood vessels and bones around the eye. This sometimes leads to difference in eye colors. Those with SWS may need monitoring for glaucoma and seizures.
– **Iris melanosis** – This non-cancerous (benign) increase in eye pigment may appear differently between eyes. It is usually stable but periodic eye exams are recommended.
– **Eye injury or trauma** – Physical damage to the eye can sometimes cause color changes months or years later due to disruption of melanin production. These eyes should be monitored closely for complications like glaucoma or uveitis.
How rare are multicolored eyes?
Multicolored eyes affect about 1% of the world’s population. Some statistics on heterochromia prevalence include:
– **Complete heterochromia** – Estimated to occur in 0.06% to 0.072% of people globally. This is around 1 in 140 to 1 in 150 people worldwide.
– **Sectoral heterochromia** -Much more common, thought to occur in around 1% of the population. This is about 1 in 100 people.
– **Central heterochromia** – Occurs in around 10% of people, or 1 in 10. Far more prevalent than complete heterochromia.
So in summary, complete or total heterochromia with one eye distinctly different than the other is quite rare at less than 0.1% incidence. However, milder forms of multicolored eyes are more common, affecting up to 10% of people when you include central heterochromia.
Is heterochromia more common in certain ethnicities?
Heterochromia appears more frequently in those of European descent and less often in African, Asian, and Hispanic populations.
Research indicates the prevalence differs among ethnic groups as follows:
– **European populations** – Estimated at 0.2% or around 1 in 500 people. Highest rate globally.
– **African populations** – Extremely rare, with prevalence below 0.1% or 1 in 1,000.
– **Asian populations** – Occurs in around 0.1% of people or 1 in 1,000.
– **Hispanic populations** – About 0.1% prevalence, or 1 in 1,000.
The discrepancy is believed to be due to genetics. The same European genes that predispose people to lighter color eyes and hair also result in higher heterochromia rates. Populations with darker pigmentation have very low occurrences.
Can animals have multicolored eyes?
Yes, heterochromia is quite common in certain animal species, especially dogs, cats, horses, and cattle. Some animals that frequently demonstrate multicolored eyes include:
– **Huskies** – Heterochromia is a breed trait seen in Siberian huskies and other northern dogs. It likely helped camouflage them in snowy environments.
– **Australian Shepherds** – Up to 10% of Aussies have sectoral heterochromia with one or both eyes marbled blue and brown.
– **Turkish Angoras** – These striking white cats often have one blue and one amber eye. Complete heterochromia occurs in about 5% of the breed.
– **Paint horses** – Common markings in Paints can produce blue and brown eyes. Patches of color on a white base lead to large sectors of heterochromia.
– **Holsteins** – The iconic black and white dairy cow often displays “odd-eyed” patterning with one brown and one blue eye.
Is heterochromia linked to deafness in animals?
Sometimes! In dogs, there is a strong correlation between heterochromia and congenital sensorineural deafness. However, this varies by breed, and not all dogs with multicolored eyes are deaf.
– Up to 22% of Bull Terriers with heterochromia are deaf in one ear.
– Approximately 18% of Australian Cattle Dogs with heterochromia have hearing loss.
– Deafness was three times more likely in mixed breed dogs with eye color variation.
While this association exists, plenty of dogs with heterochromia have perfectly normal hearing. Regular hearing evaluations are advisable for at-risk breeds.
In cats, there does not appear to be any link between multicolored eyes and deafness. No increased deafness risk has been observed in cat breeds prone to heterochromia like Turkish Angoras.
Can you have one eye that changes color?
It is possible, though extremely rare, for one eye to demonstrate iris color changes over time. This typically occurs due to:
– **Injuries** – Blunt trauma to the eye can damage the pigment producing cells in the iris. This can cause gradual depigmentation.
– **Inflammation** – Severe inflammation from conditions like uveitis can permanently lighten the iris by killing off its pigment cells.
– **Eye tumors** – Cancerous or benign tumors arising on the iris can alter its appearance and color over time.
– **Medications** – Certain glaucoma, osteoarthritis, and cancer drugs have been documented to induce color changes in the eyes as a side effect.
However, fluctuating eye color in the same eye is very unusual in the absence of the factors above. Some mythical qualities have been associated with eyes that change hues, but this phenomenon has little scientific explanation or evidence outside of true disease states.
Are people with heterochromia color blind?
No, multicolored eyes do not cause any impairment in color vision or depth perception. People with heterochromia generally see color and 3D space normally.
However, color blindness can independently co-occur with heterochromia. Color blindness is also a genetically inherited trait, so someone can coincidentally be born with both conditions. But heterochromia itself will not directly impact color vision.
Can heterochromia be acquired later in life?
In most cases, heterochromia is present at birth. But some medical conditions can cause one eye to change color post-natally:
– **Injury** – Physical damage to the eye through trauma or surgery can disrupt melanin production and lead to color changes.
– **Inflammation** – Severe long-term inflammation from iritis, uveitis, or Fuch’s heterochromic cyclitis can lighten the iris.
– **Glaucoma** – Increased eye pressure damages the pigment epithelium and causes gradual depigmentation.
– **Horner’s syndrome** – Disruption of nerves to the face reduces signaling to the sympathetic nerves in one eye causing paleness.
– **Tumors** – Both cancerous and benign tumors on the eye can alter the appearance and color of the iris.
– **Medications** – Certain medications used in cancer treatment, glaucoma, and arthritis have been associated with acquired heterochromia.
However, these cases of acquired heterochromia later in life are quite uncommon. Over 90% of people with multicolored eyes are born that way.
Famous people with heterochromia
Having different colored eyes is a unique and memorable trait. Here are a few well known actors, musicians, historical figures, and athletes who have heterochromia:
– **Jane Seymour** – British actress with one green and one brown eye.
– **Kate Bosworth** – American actress with sectoral heterochromia that makes one eye appear hazel.
– **Henry Cavill** – “Superman” actor with notable sectoral heterochromia.
– **Dan Aykroyd** – Comedy star of “Ghostbusters” and “Blues Brothers” with blue and green eyes.
– **Alice Eve** – British actress from “Star Trek Into Darkness” with heterochromia.
– **Mila Kunis** – Known for “That 70’s Show”, Kunis has profound central heterochromia with limbal rings.
– **Max Scherzer** – The Washington Nationals pitcher has sectoral heterochromia with blue and brown eyes.
– **Tim McIlrath** – Lead singer of Rise Against who has one blue eye and one green eye.
– **David Bowie** – Legendary musician Bowie’s left pupil was permanently dilated due to a teenage fight injury, appearing dark next to his blue right eye.
Can you wear an eye contact lens to mask heterochromia?
Contact lenses designed to change your natural eye color are available either for cosmetic reasons or for masking discoloration from injury. However, there are some downsides to be aware of:
– **Comfort** – Color contacts often use opaque “blocking” pigments that can impede vision and oxygen flow to the eyes. This leads to dryness and discomfort with prolonged wear.
– **Infection risk** – Any contact lens increases infection risk. But color contacts pose a greater threat since they affect air permeability and trap more bacteria. Proper cleaning is essential.
– **Eye health** – Contacts that don’t fit well or aren’t adequately oxygen permeable can cause complications like ulcers, blood vessel growth, and vision changes over time.
– **Long-term wear** – Non-prescription costume contacts should not be worn overnight or for more than short periods during the day. Long-term wear can permanently damage eyesight.
When used properly and with caution, colored contacts can temporarily transform your natural eye appearance. But they require diligent care and removal for eye health. Many opt to embrace their rare multicolored eyes just the way they are!
Conclusion
In summary, complete heterochromia with two very different colored eyes is quite uncommon, affecting less than 1 in 100 people worldwide. However partial or sectoral multicolored eyes are more prevalent, especially central heterochromia around the pupil. While a unique trait, it generally does not impact vision or health. With the proper perspective, individuals with heterochromia can appreciate their rare and special eyes.