Dog with Eye Infection

Question
My dog is 6 years old and she is a Shit-zu and Border collie mix.  She was diagnosed 2 years ago by our vet as having a tear duct problem.  She had very thick mucus on one eye only and he gave me two different kinds of meds and neither have really worked.  He also recommended using tears naturalle which I did and it hasnt helped either.  Now both eyes are inflamed and irritated and I think she may be going blind.  About a year ago, I went for a second opinion and he didnt know how to cure her either.  Do you have any ideas on this?  I was thinking it may be an allergy as we live in Florida and one winter we went to Michigan and her eye problem cleared up.  Please help?  

Answer
Without an examination, I cannot tell you what the problem is.  You should find a vet that has an interest in eye diseases.  Call around and you will find someone that has this interest.  It could be dry eyes, which will not respond to normal therapies.