Genetic Quirk Behind Maine Coon Heterochromia

Does your Maine Coon have one blue eye and another a completely different color? This dazzling condition is called heterochromia, and it’s surprisingly common in this majestic breed.

While it may look magical, heterochromia is rooted in genetics, and in some cases, it may signal other underlying health conditions, such as congenital deafness.

In this guide, you’ll learn everything you need to know about Maine Coon heterochromia, the genetic mechanisms behind it, and how it may affect your cat’s health.

What Is Heterochromia Iridis?

Heterochromia iridis (also called heterochromia for short) refers to the condition in which the eyes’ irises are different colors.

In cats, this can present as one blue eye and one eye of another shade, such as:

• Amber
• Green
• Copper

In rarer cases, a single eye may show two colors, a condition known as sectoral heterochromia.

This condition can either be present from birth due to genetic causes or acquired later in life due to injury, illness, or medication.

In Maine Coons, heterochromia is most commonly inherited and often appears in cats with white or bi-color coats.

The reason for this is rooted in feline genetics, particularly genes associated with coat color and pigment distribution.

Why Do Maine Coons Get Heterochromia?

Heterochromia in Maine Coons is typically the result of a pleiotropic gene, which means a single gene influences multiple traits.

In this case, the gene responsible for a cat’s white coat or white spotting also impacts melanin distribution to the eyes.

Melanin is the pigment that gives color to a cat’s fur, skin, and eyes. When melanin is blocked from entering one eye but not the other, the result is heterochromia.

The blue eye appears that color not because of blue pigment, but because it lacks melanin entirely, reflecting light in a way that appears blue to the human eye.

The pigmented eye, meanwhile, receives melanin and appears green, copper, or gold.

White and partly white cats are far more likely to display this trait because the white spotting gene (S) or dominant white gene (W) interferes with pigment cell migration during embryonic development.

If melanin is blocked in one eye but not the other, heterochromia occurs.

Types Of Heterochromia In Maine Coons

Not all heterochromia looks the same. There are several different types, each with its unique appearance and cause.

1. Complete Heterochromia

This is the most easily recognizable form of heterochromia. One eye is completely blue, while the other is fully pigmented. It is especially common in Maine Coons with solid white or high-white coats.

The stark contrast between the two eyes creates a dramatic and beautiful effect that often turns heads.

2. Sectoral Heterochromia

Sectoral heterochromia occurs when one eye contains two distinct colors.

For example, a cat might have a primarily green eye with a blue segment or streak. This happens when melanin is partially blocked during eye development.

Sectoral heterochromia can occur in one or both eyes and is rarer than the complete form.

3. Central Heterochromia

Central heterochromia is characterized by two different colors appearing in concentric rings around the pupil. Typically, the area closest to the pupil is one color, such as gold or hazel, while the outer ring is a different shade.

This subtle variation is often harder to detect but can create a rich, kaleidoscopic appearance in the eye.

4. Acquired Heterochromia

Unlike the genetic types, acquired heterochromia develops after birth.

It can result from:

• Trauma
• Inflammation (such as uveitis)
• Neurological disease
• Use of certain medications

If you notice a sudden change in your Maine Coon’s eye color, it is crucial to consult a veterinarian, as this can be a sign of an underlying health condition.

How Common Is Heterochromia In Cats?

In humans, heterochromia affects only around 0.05% of the population, making it exceptionally rare.

In contrast, heterochromia in cats (particularly breeds like the Maine Coon, Turkish Van, and Japanese Bobtail) is significantly more common.

The prevalence of heterochromia in felines is due to the frequency of white and piebald coloring in domestic cats.

According to the Cornell University College of Veterinary Medicine, the white spotting and dominant white genes that contribute to coat color variation are also associated with odd eyes in cats.

Are Maine Coons With Heterochromia Blind?

A common myth suggests that cats with heterochromia are more likely to suffer from blindness. Fortunately, this is not true. Heterochromia, by itself, does not affect a cat’s vision.

A Maine Coon with two different colored eyes typically sees just as well as any other cat.

The reason one eye appears blue is not due to a problem, but simply a lack of melanin. There is no structural abnormality or functional difference in the eye that would impair sight.

As long as your Maine Coon’s heterochromia is genetic and not acquired through injury or disease, there’s no need for concern about their eyesight.

Can Heterochromia Affect A Cat’s Hearing?

Although heterochromia doesn’t affect vision, it can be linked to congenital deafness in white or mostly white cats.

Research has shown that 30% to 40% of white cats with blue eyes are deaf in at least one ear.

If a Maine Coon has one blue eye, it is more likely to be deaf on the same side as the blue eye.

This happens because the same genetic mechanism that blocks pigment in the eyes and coat can also affect the development of the inner ear.

This is another example of pleiotropy, where a single gene causes multiple traits, in this case, blue eyes and deafness on the same side of the face.

Fortunately, most affected cats adapt well and live full lives, often compensating for any hearing loss with heightened sensitivity in their remaining senses (source 1).

Why White And Bi-Color Maine Coons Are Prone To Heterochromia

Cats with completely white fur usually inherit a gene called the epistatic white (W) gene, which completely masks all other coat colors and patterns.

This gene also suppresses melanin production throughout the cat’s body, including in one or both eyes.

Cats with partially white coats, on the other hand, often carry the white spotting gene (S), which restricts melanin only in certain areas.

Therefore, if one eye lies within a depigmented zone, it may remain blue while the other develops pigmentation, resulting in heterochromia.

In contrast, solid-colored Maine Coons with no white fur are far less likely to have heterochromia. When they do, it usually points to sectoral or central forms, or possibly acquired heterochromia from trauma or disease.

Cost Of Maine Coon With Heterochromia

Maine Coons with heterochromia are generally considered unusual and visually striking, making them highly desirable among cat enthusiasts.

Although breeders cannot selectively produce kittens with heterochromia, since it is not a reliably inheritable trait, cats with this feature may be priced at the higher end of the breed’s cost spectrum.

The average price for a Maine Coon kitten from a reputable breeder ranges from $500 to $2,500, depending on:

• Lineage
• Pedigree
• Appearance

A kitten with heterochromia may cost closer to $2,000 or more, particularly if they also have a white or rare coat color.

What Do Normal Maine Coon Eyes Look Like?

Even without heterochromia, Maine Coons are known for their striking, expressive eyes. Their large, slightly oval eyes are set wide apart and can be:

• Gold
• Green
• Copper
• Amber

Blue and odd eyes are accepted for white-coated Maine Coons under breed standards.

Does Maine Coon Eye Color Change?

All kittens, including Maine Coons, are born with blue eyes, due to the absence of melanin. As they grow, their eyes begin to change to their permanent color, typically by 8 to 12 weeks of age.

Once this transition is complete, eye color usually remains stable for life.

If your Maine Coon’s eye color changes after 12 weeks, it may indicate a medical issue such as:

• Inflammation
• Injury
• Tumor

Sudden or gradual color changes in adult cats should always be checked by a veterinarian.

Common Maine Coon Eye Problems

Although heterochromia itself is harmless, Maine Coons can suffer from a few eye conditions that require veterinary care:

• Conjunctivitis (Pink Eye): Causes red, swollen eyes with discharge. Easily treated with antibiotics.
• Cataracts: A clouding of the lens, common in older cats. May result in blurred vision or blindness.
• Glaucoma: Increased pressure within the eye that damages the optic nerve can cause irreversible blindness if untreated.
• Myopia/Hyperopia: Though rare, some cats may be slightly nearsighted or farsighted.
• Astigmatism: An imperfection in the eye’s curvature, which can affect focus.

Prompt diagnosis and treatment are key to preserving your Maine Coon’s vision.