Blindness

Centra I have an 8th month old male Shit Zhu, When he was born I took him to the vets when he was about 2 months old..I noticed there was something wrong with his eyes as he was always off by himself & I thought he was blind... The vet said he had progressive retinol opathy... I have been trying to find out exactly what that is!!!! sometimes I think he can see, but most of the time his head is always looking up to the ceiling!!!You would never know he is blind as he finds his way around alright but he won't come down a flight of stairs we have in our house, however he runs all over the place with his nose stuck to the ground like he his smelling his way. he is ever so cute & very healthy otherwise but was wondering if there was anything i could give him to help with his eyesight... I give him cod liver oil pills for the Vitamin A & D, which the other vet told me to do!! We live in a small town & there are no other vets to ask ... What is Retinol Opathy & can it be fixed if