A few years ago I was at a farm in Pennsylvania and there were tons of cats there that lived on the farm. My cat that I had since I was little had recently died and I really wanted to get another one. This was the prefect chance. All the cats had something in common, they were all white. I chose one of the little white kittens (he had the same colored eyes) that I was able to capture. As I was trying to catch one though, I noticed that most of the cats were fully white with the same colored eyes, but there was a handful of them with eyes that were different colors. The most common combination being one blue eye and one green eye. I always wondered what caused this coloration and if it would be related to the color of their coats. So here are a few questions that I wanted to answer in this post:
-What causes the difference in colored eyes?-Is there a connection to fur color?-Is there a likely hood that the animal will also be deaf?
This condition is called hererochromia. This is when there is a difference in coloration usually in the eye, but can be in skin or hair as well. This is not a harmful condition.
This is a result of a lack of melanin (pigment). This can be inherited, or cause by genetics, disease or injury. The odd coloring is caused when either the dominate white gene, which masks all other genes, turns the cat completely white, or it can be caused by the while spotting gene, which is responsible for the “tuxedo” look in some cats. This gene prevents melanin from reaching the eye during development of the cat, which results in one blue eye and one green, yellow or brown eye. This condition rarely occurs in cats that lack the dominant white or white spotting gene.
All newborn mammals, including cats are blue-eyes when they are born but that changes with age. A cat with this condition could simply have a light blue eye and a darker blue eye at birth, and the one eye would continuously change with age from blue to green, to yellow until it reaches the final adult color of brown. This means that this condition will never be combined without at least one blue colored eye because all mammals start off with blue eyes. From there the one eyes that lacks melanin will stay this light blue color, while the other eyes changes color as planned.
This condition is more common with several breeds such as Turkish Van, Turkish Angora, Sphinx, Persian , Oriental Shorthair and Japanese Bobtail which are all usually lightly colored cats, or have white fur combined with another color such as black or brown.
There is a common misconception that all cats with this condition are born deaf in one ear, this is somewhat true. About 60-70% percent of cats with this condition cant hear, but 10-20% of normal eyes cats are also born deaf or become deaf with age. So the chance that normal eyed cats, and odd-eyed will be deaf is not depending on the condition of different colored eyes. But white cats with one or two blue eyes do have a higher change of genetic deafness because the white gene with cause degeneration of the auditory part of their ear at birth. If a white kitten has any speck of another color on its coat, the frequency of deafness is greatly diminished. The only correlation of color and deafness would be in purely white cats, but even then cats that are not white and do not have this condition have the same likely hood of becoming deaf.
Luckily the kitten I decided to bring home with me was fully white, with a tiny black marking in between his eyes. This reduced his chanced of being deaf due to his while fur. He also had the same colors eyes and was not deaf. He is very healthy and able to hear today!