unequal pupils

I just noticed, moments ago, that my cat's pupils are unequal.  He wrestled with a robin today and I was wondering if this could be the result of an injury to his eye?  He seems to be feeling fine.

[Aleda M Cheng, D.V.M., C.V.A]

Unequal pupil size is called anisorcia.  It could be caused by trauma to his eye when your cat was wrestling the robin.  

However, the problem may have begun earlier but was too subtle to notice and may have gradually worsened over time.  This problem can be caused by anything that can affect the nervous system that innervates the eye, including trauma, inflammation, infection, toxin's and more.

If the problem continues for a couple of days, or if it worsens and/or if your cat starts to act abnormally he should be taken to his vet for evaluation and treatment.

I answered a question about anisorcia a few years ago here on medhelp. Although it does not apply to your cat specifically,  it does contain additional information if you are interested:

http://www.medhelp.org/posts/Animal-Health---General/Cats-pupils/show/224601?forums=forums