I had this problem with a fav. Its glaucoma but it can be caused my avian viral meningitis. The virus is passed from hen (who usually shows no signs) to the chick through the egg. Once the chick gets over the virus, the glaucoma will remain but it usually just clouds over and becomes non-functional while the bird lives on to be just fine. I am lead to understand that the virus does not become latent, so its okay to use the bird as a breeder, but my vet recommended that I not buy eggs from that person again.
Is that the same as when they are bug eyed though? There are photos here where their eyes are sticking out and I thought they said it was fatal?