Popeye can be caused by many pathogens and diseases. Its presence means that there is a buildup of fluid behind the eye, in the eye socket, and possibly, in other places.

About the only treatment is dosing with a broad spectrum antibiotic, either in the water or, better, injected into the eye.

I think the prognosis is poor for fish with that symptom.

I don't know of any other "unpublished" treatments like raising the temperature to fight an ich outbreak (actually, that treatment is well documented), but to echo what Tom said, keeping the disease at bay by maintaining a clean, healthy aquarium is the best way to deal with fish diseases.

Good luck!

Bill