Heterochromia in dogs - where one eye is a different color from the other - is more common that you might think, especially among breeds that carry the genes for it. This striking trait can give dogs an almost magical appearance, but what exactly causes it? There are different kinds of heterchormia, and it can even have health implications for your dog, so it's helpful to know what this condition means for your pet.
What is Heterochromia?
Basically, if your dog has this condition, the most obvious sign is that they have eyes - and specifically, irises - of two different colors. This can present in two forms: complete heterochromia, where one iris is a completely different color than the other, or partial heterochromia, where part of one iris is a different color than the rest of the iris.
It's more complicated than that, but you get the basic idea. When heterchormia occurs in dogs, it is often a genetic condition, but it can also result from a growth, or even an injury to the eye. These are uncommmon causes, however. If the cause is genetic, the genes that control melatonin distribution in the iris. Melatonin is what gives dogs - and humans - their eye color.
Not only does heterochromia appear in dogs, but also in cats, horses, and even humans.
Genetic Heterochromia
Inherited heterochromia has three different forms. Complete heterochromia, scientifically known as heterochromia iridis, is when the two irises are different colors. Dogs with complete heterochromia are sometimes called "bi-eyed." This means each iris is a completely different color. For example, a dog that has one completely brown eye and one completely blue eye has complete heterochromia.
The second form, sectoral heterochromia, is sometimes referred to as "parti-eyed." If a dog has sectoral heterochromia, this means they have two or more colors in the same iris. This variation in color could come in the form of flecks or marbling. Dogs with this type of heterochromia have segments of the iris that are different colors.
When the center of the iris is a different color than the rest, it's called central heterochromia. Instead of forming a perfect circle, the eye shows streaks or spikes of color. The colors may not seem to have any particular pattern.
The iris is the part of the eye closest to the black pupil.
Acquired Heterochromia
Acquired heterochromia is less common and can result from an injury, disease, or a condition affecting the eye. This may include conditions including:
- Uveitis: Inflammation of the uvea in the eye
- Glaucoma: A condition causing pressure build-up in the eye
- Melanoma: A type of skin cancer
Certain medications can also lead to changes in eye color. Check with your veterinarian if you dog spontaneously develops heterchormia.
Breeds That Commonly Display Heterochromia
This condition is often genetic, resulting in some breeds being more prone to the condition than others. The main reason heterchromia is more common in dogs - and other domesticated animals, for that matter - is because of selective breeding. The genes that produce this condition have been selected for, often by accident, as humans developed these breeds.
- Siberian Husky
- Australian Shepherd
- Border Collie
- Shetland Sheepdog
- Welsh Corgi
- Dalmatian
- Great Dane
- Shih Tzu
In these breeds, the genes responsible for their beautiful coats also influence their captivating eye colors, leading to the possibility of heterochromia.
Do Dogs With Heterochromia Have Hearing Problems?
There's a common misconception that dogs with heterochromia are more prone to deafness. This is partially true, but not completely. Most dogs with heterochromia are no more likely to be deaf than dogs without it.
However, dogs with merle or dappled colored coats are more likely to be deaf if they also have heterochromia. Additional confusion comes from the Dalmatian, a breed that is already susceptible to deafness, showing heterochromia.
Dogs with merle or dappled coats, who also have heterochromia, may only be deaf in one ear, rather than both. If you suspect deafness, request a hearing test from your veterinarian.
Embracing the Beauty of a Dog's Eyes
Next time you see a dog with one blue eye and one brown, you'll know a bit more about them. If they're a breed prone to heterochromia, they were likely born with it, but it can also develop after birth. They're still able to see you, just as other dogs can. And you can embrace their beauty while knowing the cause behind their unique look.
