Why Are My Cat’s Eyes Different Colours?

By Dr Duncan Houston

One blue eye and one golden eye can give a cat a striking appearance. Sometimes, different eye colours are simply part of how a cat developed.

However, an eye that has recently changed colour needs a different approach.

The most useful question is: have your cat’s eyes always looked this way, or is something changing?

Quick answer

Different coloured irises are called heterochromia. When present since kittenhood in otherwise healthy eyes, this is usually a harmless variation that does not need treatment. A new colour change, growing dark patch, cloudiness, or change in pupil size needs veterinary assessment. If the change is sudden or accompanied by squinting, pain, redness, or reduced vision, contact your vet immediately.

What is heterochromia in cats?

The iris is the coloured part of the eye surrounding the black pupil. Its colour depends partly on the amount and distribution of melanin, a pigment.

In complete heterochromia, the two irises are different colours, such as one blue and one yellow or green.

In sectoral heterochromia, one iris contains differently coloured sections, such as a blue area beside a golden area.

These patterns can develop naturally as a kitten’s eyes mature. A blue eye has little pigment in the iris; its appearance does not mean the eye is cloudy or damaged.

Heterochromia describes the appearance. Your cat’s history and an eye examination help establish whether it is a normal developmental feature or the result of disease.

How worried should I be?

Use the timing and accompanying signs to guide your next step.

What you notice	What it may mean	What to do
Different colours since kittenhood, unchanged, with clear and comfortable eyes	A normal developmental variation	Mention it at a routine vet visit, especially if the eyes have never been examined.
A new brown patch or gradual darkening of one iris	A pigment change that needs assessment	Arrange a veterinary appointment promptly. Do not wait for pain to appear.
A sudden colour change, redness, cloudiness, or squinting	Inflammation, injury, or another eye disorder	Contact your vet immediately for urgent assessment.
Suddenly unequal pupils, apparent blindness, a bulging eye, or significant injury	A potentially sight-threatening problem	Seek emergency veterinary care now.

A cat can still eat, walk around, and behave fairly normally while having an eye problem. Normal appetite does not rule out eye disease.

Can kittens’ eyes change colour normally?

Yes. Kitten eye colour develops as pigment increases during the first few months. A gradual change can be normal; sudden changes, cloudiness, redness, or discomfort need veterinary assessment.

What can cause a new eye-colour change?

A new difference in an adult cat deserves an examination, even if the eye seems comfortable.

Inflammation inside the eye

Uveitis is inflammation involving tissues inside the eye, including the iris. It can change the eye’s appearance and may cause squinting, redness, cloudiness, a smaller pupil, or a raised third eyelid.

Possible causes include injury, infection, immune-mediated disease, and cancer. Occasionally, the eye change is the first obvious sign of a problem elsewhere in the body.

Your vet needs to identify the cause and assess whether vision is at risk. Uveitis is not something to diagnose or treat from eye colour alone.

Increased pigment or an iris tumour

A brown spot or spreading dark area may be iris melanosis, a benign pigment change. However, a similar appearance can occur with feline diffuse iris melanoma, a malignant tumour.

Distinguishing these can be difficult, including for experienced clinicians. Features that increase concern include:

• Pigment spreading or changing over time.

• Thickened or raised areas on the iris.

• An irregular pupil.

• Abnormal eye pressure.

• Inflammation within the eye.

A photograph alone cannot reliably separate benign pigmentation from cancer. Your vet may recommend assessment by a veterinary ophthalmologist and a planned monitoring schedule.

Do not assume every dark spot is cancer, but do not dismiss a new spot as a harmless freckle without an examination. Early specialist assessment is recommended for pigmented iris lesions.

Cloudiness that looks like a colour change

Sometimes the iris has not changed at all. Instead, something in front of or behind it has become less transparent.

For example, a corneal problem can create a blue-grey haze over the eye, while a cataract affects the lens behind the pupil. These require different investigations and treatments.

Glaucoma, involving increased pressure inside the eye, can also cause a cloudy or bluish appearance, an enlarged pupil, discomfort, and vision loss. Acute glaucoma is an emergency.

Bleeding inside the eye

Blood within the eye can make it look red, brown, or unusually dark. Causes include trauma, inflammation, high blood pressure, and clotting disorders.

This needs urgent veterinary assessment. It should not be mistaken for a normal change in pigment.

What if one pupil is bigger than the other?

This is called anisocoria, meaning unequal pupil sizes.

The pupil is the black opening in the centre of the iris. If one pupil becomes much larger, that eye may look darker even though its iris colour is unchanged.

Possible causes include inflammation, glaucoma, injury, or a problem affecting the nerves that control the eye. Sudden anisocoria needs immediate veterinary assessment, even if your cat is not obviously painful.

Avoid repeatedly shining a bright light into the eyes to test them yourself. Tell your vet when you noticed the difference and whether it changes with lighting.

Does having different coloured eyes mean my cat is deaf?

No. Eye colour alone cannot tell you whether your cat can hear.

There is an association between white coats, blue eyes, and congenital deafness, but not every white cat with one or two blue eyes is deaf. Hearing loss may affect one ear or both, and a cat with hearing in one ear can appear to respond normally at home.

If you are concerned, ask your vet about BAER testing, which measures the hearing pathway’s response to sound and can assess each ear separately.

Clapping behind your cat or watching whether they respond to their name is not a reliable substitute. They may respond to vibration or visual movement, and hearing through one ear can conceal a problem in the other.

If deafness is confirmed, protect your cat from hazards they cannot hear. Indoor living or a secure outdoor enclosure is safer than unrestricted roaming.

When is this an emergency?

Contact an emergency vet now if your cat has:

• Sudden loss of vision or starts bumping into objects.

• Suddenly unequal pupils.

• A bulging, displaced, or visibly injured eye.

• Severe pain, repeated rubbing, or an eye held tightly shut.

• Sudden marked cloudiness or visible blood inside the eye.

These signs can involve conditions in which prompt treatment matters for comfort and vision. Do not wait overnight to see whether an obvious sudden change settles.

For a subtle, gradual pigment change without discomfort, arrange a prompt appointment rather than assuming it can wait until the next annual check.

What will the vet check?

Your vet will ask about when the difference appeared, previous eye problems, possible injuries, medications, and any other changes in health.

Depending on the findings, assessment may include:

• Comparing the irises and checking pupil responses.

• Examining the cornea, lens, and deeper structures.

• Measuring eye pressure.

• Using fluorescein dye to look for a corneal ulcer.

• Checking blood pressure or arranging blood tests when indicated.

• Referring your cat to a veterinary ophthalmologist.

The aim is to identify which part of the eye has changed and why. Treatment depends on that cause.

A healthy developmental colour difference needs no corrective treatment. An inflamed eye, pressure problem, or suspicious iris lesion needs a specific plan.

What should I do at home?

Establish whether the difference is new

Look through older photographs. A clear photo from several months ago may show whether the colour difference was already present.

However, do not delay an urgent appointment while searching through your camera roll.

Take a useful photograph

If your cat is comfortable, take a clear picture of both eyes in similar, ordinary lighting. Avoid filters and repeated flash photography.

Record the date. If your vet recommends monitoring a pigment spot, photographs taken from a similar angle can help document change. They support examinations rather than replace them.

Observe without touching the eye

Notice whether your cat is squinting, rubbing, avoiding light, or moving differently. Do not press on the eyeball or force the eyelids apart.

Avoid unprescribed eye treatments

Do not use human redness-relief drops or leftover medication from a previous eye problem unless your vet specifically advises it for this episode.

Rinsing the eye will not treat an iris pigment change, glaucoma, or an internal tumour. The useful next step is establishing the cause.

Common mistakes to avoid

• Assuming a new change is harmless because the cat is getting older.

• Confusing a cloudy eye with a naturally blue iris.

• Waiting for obvious pain before having a growing pigment patch checked.

• Assuming one blue eye proves deafness or blindness.

• Using photographs or online advice as a substitute for an eye examination.

How can I protect my cat’s eye health?

There is nothing to prevent or correct when different colours are part of normal development.

Keep up with routine veterinary examinations and familiarise yourself with your cat’s usual eye appearance. If your vet is monitoring an iris lesion, attend the recommended rechecks even when your cat seems comfortable.

The most useful habit is noticing change early: a new patch, altered pupil, persistent squint, or loss of clarity deserves attention.

Frequently asked questions

Can my cat see normally with one blue eye and one green eye?

Yes, if the difference is a normal developmental feature and both eyes are otherwise healthy. Blue eyes do not automatically mean poor vision or future blindness.

Is a new brown spot in my cat’s eye cancer?

Not necessarily. Benign pigment changes and melanoma can look similar. Arrange an examination so your vet can assess the spot and recommend monitoring or further investigation.

Can heterochromia be treated?

A harmless developmental colour difference does not need treatment. If disease has changed the eye’s appearance, treatment targets the underlying condition rather than the colour itself.

My cat’s eyes look different in photographs. Should I worry?

Lighting, reflections, and camera settings can change how eyes appear. Compare them in ordinary light and check older photographs. If the difference persists, is new, or comes with any other eye signs, arrange a veterinary examination.

Different coloured eyes can be a perfectly normal feature. A change from your cat’s usual appearance is what deserves attention, especially when it happens suddenly or affects comfort and vision.

If you are unsure whether you are seeing a normal colour difference or a new change, ASK A VET™ can help you identify what to note and discuss with your veterinarian. Painful eyes, sudden pupil changes, and vision loss need urgent hands-on veterinary care.