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Home > Cats > Iris Melanosis in Cats: Vet Approved Signs, Causes & Care

Iris Melanosis in Cats: Vet Approved Signs, Causes & Care

An orange tabby domestic shorthair cat with iris melanosis or hyperpigmentation in its eyes

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Dr. Marta Vidal-Abarca Photo

Reviewed & Fact-Checked By

Dr. Marta Vidal-Abarca

Veterinarian, BVSc GPCert (Ophthal) MRCVS

The information is current and up-to-date in accordance with the latest veterinarian research.

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Cat eyes are the most beautiful among mammals, with their vertical pupils and vibrant colors of many variations. However, like all mammals, a cat’s eye can develop medical issues that need medical attention. One such possible condition a cat can develop is iris melanosis, a feline-specific condition in which the iris develops dark, small, and flat “freckles.” This condition is typically benign, but it can turn into a malignant cancer in some cases. Let’s learn more about the condition.

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What Is Iris Melanosis?

As stated, iris melanosis is a feline-specific condition in which the iris becomes pigmented, but what does this mean? Simply put, the pigmented cells (melanocytes), which produce the melanin responsible for color in hair, skin and eyes, change. The melanocytes incorrectly replicate and spread over the surface of the iris. If this happens, the condition should be monitored closely by your veterinarian due to the possibility that the condition could turn into feline diffuse iris melanoma (FDIM), a malignant cancer. The condition could stay benign for years, but it does have the potential to unpredictably turn malignant.

Other complications could arise from iris melanoma, such as glaucoma caused by the blockage of intraocular fluid drainage. The condition usually occurs in one eye, but it can develop in both eyes. Another possible complication is the iris muscles not functioning properly if severe lesions occur, which causes difficulty for the cat to constrict the pupil in response to bright light.

Russian blue cat breed with iris pigmentation
Image Credit: Todorean-Gabriel, Shutterstock

What Are the Signs of Iris Melanosis?

Signs of iris melanosis are small brown flat freckles or “nevus” that can be seen on the iris. The coloration can show areas of brown or dark pigmentation on the surface of the iris. These spots often start out small but gradually increase in size. The condition can appear in one or both eyes. If the lesions become bumpy or raised, this is a cause for concern since it might be a sign of developing iris melanoma.

What Are the Causes of Iris Melanosis?

Pigment change in the eye causes iris melanosis. Pigment change occurs when pigmented cells (melanocytes) inappropriately spread and replicate over the iris’s surface. The main threat of iris melanosis is the possibility of the condition turning into iris melanoma. Unfortunately, there is no way of determining definitively if iris melanosis will turn into iris melanoma, which is why strict monitoring is necessary to compare any changes, such as raised lesions (lesions are benign if flat), rapid pigment increase, pupil changes, or thickening or pigment growth that spreads to the edge of the iris.

If any of these changes or “signs” occur, eye removal may be the next step recommended by a veterinarian ophthalmologist. Eye removal may seem drastic, but it’s done as a preventative measure to keep the malignancy from spreading to vital organs, such as the liver, lungs, kidneys, spleen, lymph nodes, brain, and bone, all of which can be fatal. An iris biopsy might be performed by veterinary ophthalmologists to determine if cancerous cells are present.

How Do I Care for a Cat With Iris Melanosis?

The only care available for iris melanosis is closely monitoring the condition due to the possibility it could turn into iris melanoma, which is a cancerous condition that often requires the removal of the affected eye, as mentioned above.

Monitoring is extremely vital in noting any changes so that the next best course of action can be taken. The brown spots that occur from iris melanosis will likely never resolve, but as long as the condition does not turn cancerous, your cat can still live a normal and healthy life with no pain in the affected eye.

Some ophthalmologists may recommend laser therapy that targets the destruction of the iris melanosis. However, laser treatment has not yet been proven by scientific studies to be effective.

Keep in mind that color changes with dark spots in the eye may be an inherited trait and causes no harm to your cat, but it’s imperative you take your cat to your veterinarian if you notice any changes whatsoever in your cat’s eye to be safe—never ignore changes in the eye, as color changes could indicate a more serious medical issue.

vet checking cat's eyes
Image By: santypan, Shutterstock

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Frequently Asked Questions (FAQ)

Does Iris Melanosis Spread?

Small spots may form into one large mass in larger areas of pigmentation, or the spots themselves may grow larger individually.

What Will My Vet Do If My Cat Develops Iris Changes?

Your veterinarian will perform a complete examination of your cat’s eyes that will include intraocular pressure measurement, fundus observation, gonioscopy, and ultrasound. Depending on the findings, your veterinarian may recommend a biopsy or removal of the eye (enucleation), or they will establish a monitoring protocol for you to follow. This protocol will ensure that any subtle changes in your cat’s iris are detected and melanoma, if develops, will be detected in the early stages.

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Conclusion

Iris melanosis is not a threat as long as the condition does not develop into iris melanoma. The condition causes your cat no pain or vision problems. Close monitoring and regular trips to your veterinary ophthalmologist are vital to detect any subtle changes. The first sign of iris melanosis is a small freckle in the iris that is flat and not raised. This pigmentation change can last many years before it may turn into iris melanoma, which is why close monitoring is crucial.

Remember, there is no way to tell if iris melanosis will develop into cancer, and melanoma can arise quickly and unexpectedly.


Featured Image Credit: Mary Swift, Shutterstock

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