Have Cat Questions? Ask a Cat Vet Online.
Dilation of the pupil can be caused by a lot of things, including retinal detatchment as as secondary side effect of renal failure or liver disease.
You will want to get this checked as soon as you can.
When the retinas swell, the cat can lose vision. If you catch it before the retinas detatch, you can save the site.
I hope that this helps!
Let me know if you still have questions.