a friend of mine just used this stuff called Angel Eyes,
Angels Eyes | Tear Stains | Pet Coat Stains | Eye Care For Pets | Eye Stains
Her Yorkies are 5 and 3 and have had tear stains as long as I've known them.
Completely gone. She used it for 10 days, sprinkling on their food, she highly recommends it.
When I changed Teegy's food from Royal Canin to Wellness the excessive tearing stopped, a pleasant surprise for both of us.