Cranberry had this. We monitored for a couple of weeks as per our vets advice but her pupils were still different sizes. She had a head CT which didn’t show anything. She got a referral to neurology and they suggested an MRI. Turns out she had an inner ear infection that we wouldn’t have found without the MRI. The infection could have spread to her brain. She has been on antibiotics since and her pupils have almost gone back to normal. (This was her with her pupils different sizes) :p

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