Sorry to hear that
William has Dry Eye, diagnosed when he was about 5 or so after having his tear ducts flushed a couple of times and having recurring bouts of conjunctivitis in his right eye. He is now 11 and his eyesight is still good. He has Optimmune in both eyes once a day and a check up with the ophthalmologist every 6 months.
You're doing absolutely the right thing by taking her to see a specialist. Dry Eye can cause blindness but that's more typically in undiagnosed and untreated dogs. Those who receive treatment, typically Optimmune, sometimes with the additional support of lubricating eye drops, mostly do well. So please try not to worry too much about what your vet has said. You'll know more once you've seen the specialist and hopefully the prognosis given will be more positive.
If Poppy is prescribed Optimmune again ask the vet for a repeat prescription. The ophthalmologist writes one for William that lasts 6 months and up to 6 tubes of Optimmune. The prescription costs me £13 but means that I can buy Optimmune at around £23 per tube online, a saving of about 50% 0n the amount charged by the vet. I buy it from Pet Drugs Online.
The instructions about Optimmune say to discard the tube after 4 weeks, but up to 6 weeks is safe. It was the ophthalmologist who told me that!