Can't help with the eye problem but just wanted to say that unfortunately even the best breeder can't guarantee a healthy puppy - in any breed, not just Cavaliers. I have a friend who is a really good and careful breeder of Cavaliers, but was devastated when one of her puppies developed a very serious eye problem and had to be put to sleep. Nothing hereditary, just bad luck. Buying carefully, as you did, can minimise the possibility of problems but unfortunately can't completely eradicate them. Hope you can sort the problem.
Kate, Oliver and Aled