My Comet had blasto in his right eye, and the pressure caused the retina to fully detach ..and then to rupture the eye which resulted in emergency surgery to remove the eye...all in the span of a week or so. We tried desperately to avoid the surgery and save the blind eye despite his obvious pain, but we were not successful. If I had to do it again, I would do the same thing BUT I might be tempted to try fluconazole rather than itraconazole ..or maybe both meds. Comet's eye was much more crusted over (from all the drops we were prescribed) but otherwise similar to yours. Before it ruptured, it was golf ball sized, though. Since there seems to be no research indicating that saving the eye does not necessarily inhibit successful treatment of the disease, I wonder if your vet is being overly cautious. On the other hand, my dog is not impaired at all with only one eye, and he is alive and otherwise healthy. Comet was treated with Sporanox, then generic itraconazole beaded capsules. Comet's unaffected eye received no specific treatment but was checked regularly by his optho. He has been blasto-free since 2/2008.
Many folks on this site have successfully treated with compounded itraconazole available from Pet Pharmacy and Roadrunner (both in Arizona, I think). It is MUCH cheaper. I have read, in my research, that some compounds (not necessarily those noted above) have less active ingredient (in this case itraconazole) than the labelling indicates, which is a concern. Additionally, the powder is absorbed less effectively than the beads. However, dogs have been saved with those meds, and the importance of this cannot be overstated. The FDA site I researched on the subject recommended that regular testing is advised, especially with the use of compounds, so that you know there is a high enough level in the dog's system to effectively fight the disease. Such tests are readily available from miravista labs. If your vet does not know of this, you can research the subject on the miravista labs website.
As far as expired medicines, I guess I would personally not hesitate to use them as long as they are not years past expiration. The previous owner of my house makes a very good living selling expired patented medicines manufactured in the USA to foreign locations. My .02
Best of luck
We are all rooting for you!