I doubt your dog is "done". I have a blind dog and she gets on quite well. However, I'm betting that if your dog has lost his sight to Blasto, then it's probably gone for good. However, you should really be asking your vet. Have you updated your vet with these new symptoms? I'm thinking that would be a good thing to do. First off, the dosage might not be right if the blasto is spreading, secondly, your vet might want to change medications, depending on where the blasto was to begin with, and now where it seems to be spreading.
You mention that you're putting drops in his eyes, that makes me think the vet knows about this. Some dogs have had their meds changed from Itraconozole to flucanazole if the blasto is in the eyes and such. But this might not be right for your case. In any event it might be a good thing to mention to your vet.
We could probably discuss what has been working for us, if we knew a little more about your particular case. What kind of dog? How much does he weigh? what dose of itra is your dog on? Things like this might make it easier for us to compare what we know to have worked or otherwise.