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Heterochromia

Have you seen ever seen a Husky with two different colored eyes? If you have answered yes, then you have seen an animal with Heterochromia. Dogs, cats, horses and people can have heterochromia. This condition is caused from a lack or excess of melanin (a pigment found in hair, eyes and nails). The term for too much melanin is hyperchromic. Hypochromic is the less than normal amount of Melanin. Although, heterochromia can develop after an injury or illness, genetics is the major player for heterochromia in animals. Acquired heterochromia happens due to inflammation, injury and some brain tumors that may alter the iris color. Usually animals born with heterochromia have inherited this trait from a parent – this is called congenital heterochromia. Some studies have shown that congenital heterochromia is caused from a lack of genetic diversity.

 

Dogs that have the merle or piebald colorations are more prone to having heterochromia. There are certain dog and cat breeds that are more inclined to have this condition as well. Huskies, Malamutes, Great Danes, Dalmatians, Border collies, Shetland Sheepdogs, Dachshund, Chihuahua, Shih Tzu, Catahoula leopard dogs, and Australian Shepherds are the dog breeds we usually see this happen in. Turkish Van, Japanese Bobtail, Turkish Angora and Khao Manee are just a few cat breeds with it. But mixes and mutts can have this trait as well – just like my boy, Harvey.

 

There are different types of heterochromia as well. Complete heterochromia is when one eye is totally blue and the other eye is a totally different color. This corgi has complete heterochromia.

 

Partial heterochromia or (heterochromia iridis) is the term used when the same iris has different areas of color pigmentation. This husky has partial heterochromia – notice the brown eye with the blue spot.

 

Not only does heterochromia effect eye color, it can cause two-toned nose color as well.

Culture Beliefs about heterochromia

The Native Americans held dogs with heterochromia in high regards. They called this condition”ghost eyes” due to their belief that the blue eye held the ability to see into the heavens and the other eye saw all things related to the earth.

 

Health concerns

A majority of people have heard, and believe, that animals that with a blue eye (or eyes) are deaf and others believe the animal is blind in the blue eye. These beliefs are not necessarily true. There are some higher probabilities of deafness related to colorations and breeds but it is more of a coincidence due to those same breeds and colorations are prone to heterochromia. For example, Dalmatians are highly likely to be born deaf and, due to their markings, they can have heterochromia. There have been studies that have shown merle and piebald dogs have a genetic marker within those colorations that is linked with deafness. Those same genes that make up the merle and piebald – like I mentioned earlier – tend to have a higher incident of heterochromia. Basically, this means the color genes decide deafness and heterochromia – not the heterochromic gene decides the deafness. Again, coloration in white cats plays a huge role in whether they are deaf. Here is an interesting chart with white cats and their eye color statistics:


White cat – non-blue eyes

17-22% born deaf


White cat – one blue eye

40% born deaf


white cat – both blue eyes

65-85% born deaf

 

Another concern people have is that the heterochromic pet is blind in the lighter colored eye. Most of the time, this isn’t the case. Due to the lack of any pigmentation in the blue eye, our own eyes see light reflect off the back of the eye and it creates the blue-ish color.

 

If you ever notice a change in your pet’s eye(s), schedule a visit to the vets. It can be an indication that there is an issue with your pet.

 

If you happen to be one of the special people who gets to share their life with a heterochromic pet, relax and enjoy life with one of these unique and beautiful creatures.

 

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