Toxoplasmosis is no joke.
When they looked closer, they could see the tracks of the organisms burrowing and making tracks in his retinas.
He was there for a week, and when we were visiting, one of the professors would come in with a few students to have them look at the retinas of our cat so they could see first hand what it looked like, since it is relatively rare. He did get better, and it wasn't as expensive as we thought to have him diagnosed and treated. He was such a good cat, I did miss him when he finally left us. This is a picture of him guarding my car from Massachusetts liberal vandals: