You can use Visine, it won't hurt the dog but it won't help her either. There is really no medicinal value to Visine except that it gets the red out. Same thing with an eye wash, it may help to rinse away dirt but won't help the cause of the problem Runny eyes can be caused by almost anything. Some that come to mind are allergies. Ingrown eyelashes or eyelids that turn in slightly can also cause problems and left untreated can lead to major problems upto and including ulcerations or secondary glaucoma. I know you have gone to 3 different vets, but who you really would need to see is a board certified canine opthalmologist. Going to your vet is like us going to our family doctor, they are experts in many areas but they are specialized in none. Ask one of the vets that you trust to recommend a canine opthalmologist. Even if you might have to drive a ways to see one it would be well worth the trip and they aren't all that more expensive. The have the specialized tools to work with and are on the cutting edge of technology. I'm lucky here in NY that I am fairly close to the Cornell School of Veterinary Medicine. Keep us updated on how you make out.
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Bob
If there are no dogs in Heaven, then when I die I want to go where they went.