Ok, so I took all of your advice and took him into the vet today. He said that it is probably a liver shunt, which means that his food is not getting digested properly and the proteins are turning to ammonia and getting into his brain. This is causing the seizures and the eyesight issues.
We are going back in tomorrow to run some tests and see what we can do about helping him out.
Thank you so much for all of your replies. I'm really glad we took him in.