Dark Spots (Iris Melanosis) in Cat’s Eye

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What are brown spots in the eye?   What do they look like?    When to see a veterinarian?   Treating dark spots in the eye

Brown spots in cat's eye

What are brown spots in a cat’s eye?

Medically known as iris freckles, iris freckles, iris hyperpigmentation, melanoma and iris melanosis, as the name would suggest, brown spots occur in the iris (the coloured part of the eye) and are reasonably common. They are similar to moles or pigment spots and are seen most often in cats who are middle-aged to senior.

The condition is caused by the proliferation of melanocytes, which are cells responsible for the production of pigmentation. For the sake of simplicity, we will refer to the benign form as iris melanosis and the cancerous form as malignant melanomas.

Dark spots can develop in cats of any eye colour and may be cancerous (malignant) or benign. It is also possible for a benign iris melanosis to slowly progress into a malignant melanoma, although this is quite rare. More often than the above, iris melanomas lead to glaucoma, a condition caused by an increased pressure within the eyeball. Glaucoma causes distorted vision and can be extremely painful. Malignant melanomas have the potential to metastasize (spread) to other parts of the body, especially the lungs and the liver.

What do these brown spots look like?

Brown spots in cat's eye

Areas of dark brown pigmentation within the iris. There may be one or multiple areas of pigmentation. Spots usually only occur in one eye but in some cases, both eyes can be affected. Spots may start out small and gradually increase in size and become darker. Where multiple spots are present, as they increase in size, they may merge together.

An iris melanosis is flat and should not protrude above the surface of the iris. Malignant melanomas are lumpy, raised and can cause distortion to the surface of the eye.

While iris melanosis is painless, if infiltration of the neighbouring drainage angle occurs, glaucoma, an extremely painful increase in intraocular pressure can develop. 

When to see a veterinarian:

Iris melanosis in cats

A veterinarian should evaluate pigmented spots in your cat’s eye to determine if they are benign iris melanosis or a malignant melanoma.

Tests he will perform may include:

  • A slip lamp examination to check the eye under magnification.
  • Fine needle biopsy to determine if the lesion is benign or cancerous.

Your veterinarian may refer your cat to a specialist eye veterinarian, (known as an ophthalmologist) for diagnosis and treatment.

Treating dark spots in cat’s eyes:

Brown spots in cat's eye

  • A wait and see approach recommended for cats with iris melanosis. You will need to regularly check your cat’s eye(s) to make sure the spots aren’t growing in size.
  • Re-assessment by a veterinarian every six months, with comparison photos taken.
  • Destruction of the cells with a laser or removal of the entire eye are the treatment of choice for malignant melanomas.
  • Removal of the eye may be necessary if glaucoma has developed.

9 COMMENTS

  1. I adopted a sibling pair last nov 2017, the female came with one of these.
    they both has horrible start in life but living a wonderful live now. I hope this does not become an issues its been 8 months since I adopted them and both are thriving very well.. so happy too, they make my life!! I love my 3 ragdolls with in 3 years so not sure if I was ready for another, but these two needed me!! I do feel my last past ragdoll brought them to me.. long story lol

  2. My 10 year-old cat has two of these brown spots in her left eye. The first appeared 5-6 years ago and it is still there. A month ago I noticed the second brown spot. She acts normal and I’m hoping it is nothing cancerous. We will be going to our vet to get it checked out.

    • Always good idea to get these things checked out. The vet can make a note of the size and shape and monitor. I’d also recommend you take photos and date them so you, too can monitor and see the vet if anything changes.

  3. My cat is only a year and half and she has these spots on her right eye. I’ve noticed she doesn’t react the same on her right side with affected eye. I did motion tests on her waving my hand and it seems like she doesn’t see at all. I’m very concerned and planning a trip to the vet, but will her eye be taken out?

  4. Freckles maintain the texture and look of other areas. Only the color changes.

    Melanoma has irregular texture, different from the normal one.

    Of course, this also applies to humans.

  5. its not in a cats eye. its growing very fast in my eye. strange shape and i lost my vision in that eye a while ago. should i go to the vet even though im a person? or will a human doctor know what this is. the shape is like the melinoma skin cancer my brother died of three years ago but his was on his skin. my brother didnt start getting sick until he went to the doctor so i might not say anything and just wait and see with my good eye if it gos away.

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