I'm sorry to hear about your babies eyes, I don't think seven is old... you have plenty of years to play, snuggle, and put eye drops in
Whenever I'm at the vet it seems like there are a lot of tests to be done too, even with healthy dogs, it's not like treating a person where they can talk to you and tell you symptoms. Actually dogs tend to hide their pain. So I think a vet needs to do testing to make sure they aren't missing anything. I'm not a vet it's just my line of thinking, however I too have been surprised at a bill hmm never in a good way
I hope you get some more info on the dry eye. I know my grandma (a human) has it and she has drops and flare ups when the weather changes, but I don't know anything about a dog having it.
Hugs to baby and you