Very effective cure for blocked tear ducts (for the brave only) is the juice of a white onion.
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It wasn’t blocked by some foreign obstruction, it was grown over with her own tissue. The vet said that he stuck a thin, hot glass rod through the thing, and that opened it up and cauterized it at the same time. But her eye was damaged from being dry and inflamed for so long, and although she wasn’t blind, she always had a slight-to-severe squint in it.