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Dr. B.
Dr. B., Board Certified Veterinarian
Category: Vet
Satisfied Customers: 22615
Experience:  General practice veterinary surgeon with extensive experience in a wide range of species.
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My 12 year old cat has green eyes but her left eye has changed

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My 12 year old cat has green eyes but her left eye has changed colour during the past year to a yellow/brown colour. She is not bothered but should I be concerned?

Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.


Can you tell me if the discolored iris looks smooth like the other eye?

Any ridges, bumps or changes in texture visible?


Any changes of color to the clear corneal covering the eye?


Any redness of the blood vessels at the top of the eye?


Any color changes anywhere else within the eye?

Customer: replied 4 years ago.
No bumps - very smooth. No red blood vessels. Clear cornea.

Thank you,

Now as I am sure you can appreciate, eye color isn’t something that naturally changes in adult animals. Often the colour the eye is at 3 months of age will be the color of that cat’s eye for life. Now to see changes, especially in only one eye, does raise red flags of concern here. Even if this is not bothering her, we do need to be pro-active and cautious here (since often we don't see it disturbing the cat until the condition is advanced). And there can be a range of reasons for an eye to change color. Now if her cornea looks normal and you are only seeing color change at the iris and not a diffuse color change (affecting all of the eye), then issues like corneal disease, uveitits (an inflammation/infection within the eye that often causes yellow/red color changes), or bleeding into eye would be less of a concern here.

If we consider iris changes that could be responsible for what you are seeing then again there are a few considerations. The first is a benign process that we can see in old cats is "iris degeneration." When this arises, we see the iris become moth eaten in appearance. Now this would be common at her age but we'd expect the underlying color of the eye to remain the same and both eyes to be affected similarly.

Since this is not the case and the color is yellow/brown, we do have to be concerned about pigment cell (melanocyte) based issues. Now I am glad that you are not seeing an obvious growth on the iris since that would raise concerns nasty cancers Still we cannot completely rule out this sinister differential. Especially as we can see pigmented areas appear that are flat, which we call iris melanosis. These are often benign but can convert to a malignant tumor (melanoma) or be associated with glaucoma problems in the affected eye. Furthermore, we can also see melanomas that are flat, therefore we do have to proceed with caution here. You can see some examples of the variety of appearances these cancers can have here (example- solitary; - diffuse, - severe diffuse ). As you can see some will look mass like but others can be quite subtle and unassuming.

Overall, if you have been seeing progressive brown pigmented changes arising in one eye, then I'd advise you do want to have this checked out for her. If this is a subtle melanoma, they can continue to grow and even if they are benign (thus not spreading in the body) they can still cause problems like glaucoma (since there is only so much space in the eye and their presence increases the intraocular pressure and impedes drainage of the eye’s fluid).

In this case, it would be worth seeing your vet about you lass's eye. If they feel that this isn't just iris degeneration, then you might wish to discuss having a veterinary ophthalmologist examine her eye (Since they will more adept at differentiating between the potential causes though this might not be possible without a sample of the tissue). This way you will be in the best position to identify what this is, and address what is present before it gets to a critical stage for her.

If you do need to find an ophthalmologist, then you can find one via the RCVS Register (HERE) or contacting your local veterinary school.



I hope this information is helpful.

If you need any additional information, do not hesitate to ask!

All the best,

Dr. B.


If you have any other questions, please ask me – I’ll be happy to respond. Please remember to rate my service once you have all the information you need. Thank you and hope to see you again soon! : )


Customer: replied 4 years ago.
Thank you. Your answer was really helpful. We need to take her to the vet as I think she has a melanoma.
You are welcome.

I do think that is the best course of action here. Hopefully, it will just turn out to be melanosis but knowing sooner rather then later is always the best policy with eye based issues of this nature.

Please take care,

Dr. B.


If you have any other questions, please ask me – I’ll be happy to respond. Please remember to rate my service once you have all the information you need. Thank you and hope to see you again soon! : )

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