Expert: Jessica - 3/14/2010

Question
I have an 8 year old mixed breed cat.  For the last year part of the pigment in her yellow iris is turning brown.  It is not red and the eye isn't swollen.  Do you have any idea what could be causing this?

Answer
Hi Laura.  I can't say for certain, but I think there's a very good possibility your cat has uveitis, an inflammation of the middle globe of the eye.  One of the most common signs of uveitis is that the iris begins to turn a dull rusty color, and this is because red blood cells are accumulating right over the iris.  If you do an image search for feline uveitis, you will find some pretty outrageous photos, but here is a picture that is closer to your average case:

http://www.perplexcats.nl/content/aboutcats/images/felv2.jpg

The causes of uveitis can range from a deep, penetrating trauma to a systemic infection, such as feline leukemia or toxoplasmosis.  I recommend to have your kitty tested for the feline leukemia and feline AIDS viruses if she has never been tested or if she goes outdoors, since these are two common causes of the condition.  However, there is often no known cause of uveitis.  The treatment consists of an antibiotic eye drop or ointment.  As long as the eye is not scratched or ulcerated, a steroidal drop or ointment will be prescribed as well, since the condition is painful, and the steroid will reduce pain and inflammation.  It's important to treat this aspect, since the inflammation associated with uveitis can lead to complications such as glaucoma, luxated lens and detached retina in some cases.

Even if your kitty's eye doesn't resemble the picture of uveitis, I would urge you to get her to the vet.  No pigment change in the eye is normal after 8-12 weeks of age.

Good luck!

Jessica