Why Are My Dog’s Eyes Different Colours?

By Dr Duncan Houston

One blue eye and one brown eye can be a completely normal feature in a dog. Some dogs also have two colours within the same eye.

The important distinction is whether the eyes have looked that way since puppyhood or whether one has recently changed.

A lifelong colour difference is often harmless. A new change deserves a veterinary examination.

Quick answer

Different coloured irises are called heterochromia, and dogs can inherit this as a normal variation. If the pattern has been present since puppyhood and both eyes are healthy, it usually needs no treatment. A new colour change, cloudy appearance, growing dark patch, or unequal pupil size needs veterinary assessment. Sudden changes, pain, squinting, redness, or reduced vision require urgent advice from your vet.

What is heterochromia in dogs?

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

There are two main patterns:

• Complete heterochromia: the irises are different colours, such as one blue and one brown.

• Sectoral heterochromia: part of an iris is a different colour, such as a blue section within a mostly brown eye.

These patterns can occur naturally and have genetic causes. Research in Siberian Huskies, for example, has identified a genetic variant associated with blue eyes and heterochromia.

Heterochromia describes the colour pattern. It does not, by itself, establish whether the eyes are healthy.

Are some breeds more likely to have different coloured eyes?

Yes. Different eye colours are familiar in Siberian Huskies and Australian Shepherds, and can also occur in other breeds and mixed-breed dogs.

There is more than one genetic route to blue eyes. Merle coat genetics can produce blue or partly blue eyes, while the blue-eye trait identified in Huskies has a different genetic basis.

This matters because a blue eye does not automatically mean the same thing in every dog. Coat pattern, ancestry, hearing, and the structure of the eyes all help your vet interpret the finding.

How worried should I be?

What you notice	What it may mean	What to do
Different colours since puppyhood, unchanged, with clear and comfortable eyes	Normal inherited variation	Mention it at a routine examination if the eyes have never been checked.
A new pigment patch or gradual change in iris colour	A pigment change, inflammation, or a growth	Arrange a prompt veterinary appointment.
A gradual blue-grey haze in an older dog	A lens change such as nuclear sclerosis or cataract	Book an examination to identify the cause.
Sudden cloudiness, redness, squinting, or an eye held closed	A painful or potentially sight-threatening problem	Contact your vet immediately for urgent assessment.
Suddenly unequal pupils, apparent blindness, a bulging eye, or significant injury	An eye emergency	Seek emergency veterinary care now.

Do not rely on appetite or enthusiasm for a walk to judge eye health. A dog can compensate for reduced vision in one eye, and discomfort may be subtle.

Can a puppy’s eye colour change normally?

Yes. Eye colour can develop as a puppy matures, so a young puppy’s appearance may not be their final adult colouring.

Gradual development in clear, comfortable eyes can be normal. However, redness, cloudiness, discharge, or squinting should not be dismissed as part of growing up.

If you are unsure, ask your vet to examine both eyes during the puppy’s health check.

What can cause a new eye-colour change?

An adult dog developing a new difference needs assessment. The change may involve the iris, the clear front surface, or the lens inside the eye.

Inflammation inside the eye

Uveitis is inflammation affecting tissues inside the eye, including the iris. It can alter the eye’s appearance and cause redness, squinting, sensitivity to light, cloudiness, or a smaller pupil.

Causes include trauma, infection, immune-mediated disease, and occasionally tumours. Some dogs need investigations beyond the eye because an underlying illness may be responsible.

Treatment depends on the cause. Without appropriate care, complications can include cataracts and glaucoma.

A new dark patch or growth

A new brown or black area may represent a pigment change, a cyst, or a tumour.

In dogs, many primary pigmented tumours arising within the eye are benign melanocytomas. However, benign does not mean a lesion can be ignored: a growing mass can still interfere with eye function or cause inflammation and glaucoma. Malignant tumours also occur.

Features that warrant particular attention include:

• A patch that enlarges or changes.

• A raised lump.

• Distortion of the pupil.

• Bleeding, redness, or discomfort.

• A change in vision.

Your vet may recommend a veterinary ophthalmologist to distinguish the possibilities and decide whether monitoring, further testing, or treatment is appropriate.

Do not diagnose a new spot as a harmless freckle from a photograph.

Glaucoma

Glaucoma involves increased pressure inside the eye. It can cause a cloudy appearance, redness, an enlarged pupil, pain, and vision loss.

Some dogs have an inherited predisposition. Others develop glaucoma secondary to another problem, such as inflammation, a displaced lens, or a tumour.

Acute glaucoma needs immediate treatment. Waiting to see whether the appearance improves can reduce the chance of preserving vision.

Bleeding inside the eye

Blood can make an eye look red, brown, or much darker than usual. Possible causes include injury, inflammation, clotting disorders, high blood pressure, and tumours.

Visible blood inside the eye needs urgent veterinary assessment. It is not a normal change in eye colour.

Why is my older dog’s eye turning blue or grey?

A blue-grey appearance in an older dog often comes from the lens behind the pupil, rather than the iris.

Two important possibilities are nuclear sclerosis and cataracts.

Nuclear sclerosis

Also called lenticular sclerosis, this is an age-related change in which the lens becomes denser and develops a translucent blue-grey haze. It typically affects both eyes and usually does not cause major vision loss.

It does not generally require treatment, but an examination is needed to confirm the diagnosis and check for other problems.

Cataracts

A cataract is an opacity within the lens that can interfere with vision. Cataracts can be inherited or associated with problems such as diabetes, injury, or inflammation.

Diabetic cataracts can develop quickly, so new cloudiness or reduced vision in a diabetic dog deserves prompt attention. Cataracts can also cause secondary inflammation and glaucoma.

Do not assume a cloudy eye is simply old age. Nuclear sclerosis, cataracts, and other eye disorders can look similar to an owner and may occur together.

What if one pupil is bigger than the other?

Unequal pupil sizes are called anisocoria.

The pupil is the black opening in the centre of the iris. If one pupil becomes larger, that eye may look darker even though its pigment has not changed.

Causes include eye inflammation, glaucoma, corneal injury, and problems affecting the nerves controlling the eye. Sudden anisocoria requires immediate veterinary assessment, including when it is the only obvious change.

Do not repeatedly shine a torch into the eyes to test them. Let your vet assess their responses safely.

Does having different coloured eyes mean my dog is deaf or blind?

No. A dog can have different coloured eyes and normal hearing and vision.

However, some pigmentation-related genetic conditions are associated with hearing loss or abnormal eye development. Certain merle combinations, particularly double merle, carry increased concern for these problems. Eye colour alone cannot establish the dog’s genetic status or diagnose a disability.

If there are concerns about hearing, your vet may recommend BAER testing, which checks the hearing response of each ear separately. Responding to a noise at home does not reliably exclude deafness in one ear.

An eye examination assesses vision and eye structure. A genetic result, hearing test, and eye examination answer different questions.

When is this an emergency?

Seek emergency veterinary care now if you notice:

• Sudden loss of vision or bumping into familiar objects.

• Suddenly unequal pupils.

• A bulging, displaced, or visibly injured eye.

• Severe discomfort or an eye held tightly closed.

• Sudden marked cloudiness or visible blood inside the eye.

A newly red or squinting eye also deserves urgent assessment. Eye disease can progress before the dog appears generally unwell.

For a gradual pigment change without pain, arrange a prompt appointment rather than waiting until the next annual vaccination.

What will the vet check?

Your vet will ask when the change appeared, whether it is progressing, and whether your dog has previous eye disease, diabetes, injuries, or current medications.

Depending on the findings, the examination may include:

• Comparing the irises and checking pupil responses.

• Examining the cornea, lens, and back of the eye.

• Measuring eye pressure and tear production.

• Applying fluorescein dye to check for a corneal ulcer.

• Checking blood pressure or arranging blood tests when indicated.

• Referring your dog to a veterinary ophthalmologist.

The aim is to identify which structure has changed and whether the problem is limited to the eye.

What should I do at home?

Compare with older photographs

Look for clear pictures showing whether the difference existed previously. This can help establish the timeline.

Do not delay urgent treatment while searching for the perfect comparison photo.

Record changes clearly

If your dog is comfortable, take a photograph of both eyes in ordinary lighting. Keep the date and avoid filters.

For a lesion your vet has chosen to monitor, use a similar angle and lighting each time. Photographs help document change, but they cannot measure pressure or replace an examination.

Prevent further irritation

Discourage rubbing and keep your dog away from rough play while arranging care. Ask your vet whether a protective cone is appropriate.

Do not press on the eyeball or force the eyelids apart.

Avoid unprescribed drops

Do not use human redness-relief drops or leftover eye medication unless your vet specifically recommends it for this episode.

Different eye problems can require very different treatments. Something prescribed for a previous condition may be unsuitable now.

Common mistakes to avoid

• Assuming every blue eye is healthy because some breeds naturally have them.

• Calling new cloudiness an age change without an examination.

• Waiting for obvious blindness before seeking help.

• Assuming a dark iris patch must be cancer or must be harmless.

• Using eye colour to diagnose hearing loss.

How can I protect my dog’s eye health?

Normal inherited heterochromia does not need correcting.

Keep up with veterinary checks and learn what your dog’s eyes usually look like. If your vet recommends monitoring a pigment lesion or lens change, attend the rechecks even when your dog seems comfortable.

For dogs with known inherited eye risks, ask whether specialist screening is appropriate. Report new squinting, redness, cloudiness, or changes in vision promptly.

Frequently asked questions

Can my dog see normally with one blue eye and one brown eye?

Yes, when this is a normal inherited feature and both eyes are otherwise healthy. Colour alone does not establish how well either eye sees.

Does heterochromia mean my dog is part Husky?

No. It occurs in several breeds and mixed-breed dogs through different genetic pathways. Eye colour is not a reliable ancestry test.

Can different coloured eyes be treated?

A harmless inherited difference needs no treatment. If disease has changed the appearance, treatment is directed at the cause rather than making the colours match.

Why do my dog’s eyes look different in photographs?

Lighting, camera settings, and reflections from inside the eye can change their appearance. Compare them in ordinary light. A persistent new difference, cloudiness, or any discomfort still needs an examination.

Different coloured eyes can be a normal feature of your dog. A new change in colour, clarity, pupil size, or comfort is what should prompt action.

If you are unsure whether your dog’s eyes show a normal variation or a new problem, 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.