It might also be worth you while to ask your Vet for the name of an eye specialist and have him checked out. A regular Vet is not qualified to do full eye exams.
Is the pup registered? or did he come with registration papers? And as for telling you it was OK to take him at 5 wks, those people should be reported to animal control, because as stated in is not legal in California (or many other states) to sell a puppy at less then 8wks.
Would love to see pictures.
And it is really important that you have him DNA tested for Fanconi… that way you know the situation for the future.