A couple of years ago we adopted an older Spanish podenco who was blind. His eyes are cloudy blue, but we believe he can see shadows. He amazes us with how he finds his way around life, using his ears and nose. e's even learned to walk up the ramp into the back of the car. Our suspicion is that his blindness is the result of an eye infection untreated - we know how bad the Spanish hunters are at looking after their dogs, especially if it involves vet fees.
This weblnk takes you to an interesting article about blindness in dogs.
And I would say to any readers - if your dog starts losing its sight, it is nothing to be concerned about, the dog will cope amazingly well. And use a Blind Dog harness, it's a great conversation starter and a good way to tell people about galgos!