A good breeder would do know the problem exists in the breed and do the tests for CEA before breeding, regardless of how good the dogs were at working. A blind collie can't work!
I am so sorry this has happened to you, Sabrina, but your vet would only check the pups for hereditary defects if eh thought they wouldn't have been tested for. vets, like Joe Public, assume that breeding is done by knowledgeable people. Unfortunately they are wrong much of the time.
He will be loved, that is what matters, and his other senses will make up for a lot of his loss of vision. I'm sure you will still have a lot of fun with him.