What causes heterochromia in cats?
All kittens are born with eyes that appear blue due to a lack of pigment within the iris. Within their first few weeks/months of life a pigment called melanin is distributed throughout the iris, causing the eyes to change colour. Usually this happens in both eyes, but if the cat has heterochromia, melanin is only distributed in one iris, leaving the other blue.
It isn’t clear what causes some cats to develop heterochromia and others not. It appears to be a developmental condition and while there could be a genetic link, nobody really knows what causes this strange and beautiful phenomenon. While some breeds of cat seem more likely to develop heterochromia than others, it can happen to any cat.
Do odd-eyed cats have poor eyesight?
Luckily, heterochromia doesn’t have any impact on a cat’s ability to see, and it doesn’t seem to affect their hearing either. Although white cats with one or two blue eyes are more likely to be deaf, non-white cats with one blue eye do not appear to have a higher risk of deafness than normal.
There’s only cause for concern if your cat’s eyes change colour when they are over 12 weeks old or if they suddenly change colour at any age. There are various disease processes that can cause an eye to change colour and, if this happens, then you should speak to your vet as soon as possible.
Can cats have a single eye with two different colours?
When cats have two different coloured eyes this is known as complete heterochromia, but there is also a condition known as sectoral heterochromia. This is when a single iris contains two or more colours, eg half is blue and half is green, and is a result of an inconsistent distribution of pigment within the iris.
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For more amazing facts about cats’ eyes, read our blog post.