Cats eye colour changing: White cat with one amber and one blue eye

Heterochromia, where a cat has odd-eyes, most commonly occurs in cats with white fur.

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Why is my cat’s eye colour changing?

By Greta Inglis Dog Behaviourist | Animal Behaviourist

Updated on the

The eyes are the window to the soul, but they can also tell us about our pet's health. Here we look at what your cat's eye changing colour might mean.

Most kittens are born with blue eyes, but while some breeds, like the Siamese cat breed, will keep their baby-blue appearance, most cats’ eye colours will change. From three to eight weeks, just as their sight develops, a cat's eyes may change depending on the amount of melanin in the iris. The darker the pigment, the darker the eye will be. Your kitten's eyes could change from green or brown to even hazel.

How will I know if my adult cat will have blue eyes? 

Melanin production determines whether your cat will have blue, yellow, copper, or green eyes. By the time your kitten reaches seven weeks old, its adult eye colour will start to emerge, and by three months old, you will know exactly what colour its eyes will be. If the melanin production in the iris increases, it can lead to darker hues. As cats get older, the melanin levels can fluctuate due to environmental influences or genetic factors. This can cause slight shifts from blue to green, yellow, or amber eyes. 

What does a sudden change in cat eye colour mean? 

While most cats have two eyes of the same colour, odd-eyed cats are not uncommon. This striking appearance, known as heterochromia, is most commonly seen in cats who possess the white spotting gene, which is responsible for white patches, bibs, and socks. Heterochromia is often a result of variances in melanin distribution or genetic factors. Cats can be born with heterochromia or develop it over time.

If your cat's eye has changed colour suddenly, this may indicate a health issue that needs looking into. 

9 health problems associated with a change in the colour of a cat's eye

If your cat's eye changes colour, it's natural to worry that an underlying health condition is responsible. Here, we look at nine reasons a cat's eye can change colour.

1. Uveitis

Uveitis is caused by an inflammation of the uveal tract of the eye, which can result in the protrusion of your cat's third eyelid. This can be a symptom of diabetes, high blood pressure, or a bacterial infection.

Uveitis can cause your cat's eyes to look red or cloudy, and the condition will need veterinary treatment. 

2. Portosystemic liver shunt

While copper eyes can be natural, they may also indicate that your cat suffers from a portosystemic liver shunt. This is a blood vessel anomaly that causes blood from the abdominal organs to be diverted to the heart. By bypassing the liver, toxins can't be cleared from circulation. 

3. Jaundice

Jaundice, caused by obstructed bile ducts, discolours the skin and can also lead to discolouration of the eyes, which may make your cat's pupil look yellow. 

4. Bacterial infections

Feline viral rhinotracheitis and feline calicivirus are fairly common among our feline friends. If your cat has a cold, their eyes may become red from irritation and rubbing.

5. Corneal ulcers

Corneal ulcers are most commonly caused by blunt trauma, often caused by an accident or a fight. Recurrent feline viral rhinotracheitis can also lead to ulcers, which may result in a milky eye colour or a redness to the eye. 

6. Conjunctivitis 

Perhaps one of the more common complaints to the eyeconjunctivitis is caused by an inflammation of the thin mucous membrane. Symptoms include a watery green or yellow discharge, which may need to be treated with antibiotics.

7. Glaucoma

Glaucoma is caused by increased pressure in the eye, and if left untreated, it can cause loss of sight. A key symptom to look out for is a cloudy white, milky eye. If your cat's eye has changed colour this way, it's worth booking a visit with your vet to rule out glaucoma. 

8. Entropian

Entropian is an abnormal rolling in of the upper or lower eyelids. Irritation can cause scratching and redness to the cornea, as there will be painful irritation to the eye's surface. 

9. Eosinophilic Keratitis

This is a chronic inflammatory condition caused by a type of white blood cell invading the cornea. It can cause the eye's surface to appear pink, white or grey. Long-term, anti-inflammatory medication will most likely be required. 

Do cats' eyes change colour with mood? 

While this may be a commonly held belief, it's unlikely that your cat's eye has changed colour because of their mood. In reality, it's more likely because the tissue behind the cat's retina reflects light in a way that makes the pupil glow. In cats with yellow eyes, this will usually look green, and in blue-eyed cats, it will usually look red. 

Do cats' eyes change colour when they die?

If you've experienced the sad death of a beloved pet, you may have wondered what happens to its eye colour when it dies. While it may seem as if the eye changes colour, this isn't the case. After death, your cat's eye will become cloudy in appearance, gradually turning opaque over time. 

While kittens' eyes change colour as they grow, a sudden change in the eye colour of an adult cat may indicate underlying health conditions. It's always worth speaking to your vet to ensure your cat is as happy and healthy as possible. 

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