It works wonderfully for my Shih Tzu. He only seems to have issues in spring and fall, so I'm assuming his staining is related to a little extra watering due to allergies. A few weeks on Angels Eyes clears it right up, and then I stop until needed again.
FWIW -- One of the more natural remedies often mentioned for eye staining is powdered buttermilk. After I got my Shih Tzu's cleared up last fall with Angels Eyes, I immediately started giving him a half teaspoon of powdered buttermilk a day. It may be a total coincidence, but so far this spring he's had no staining. By this time last spring I'd started him on Angels Eyes.
Me, DH and Yogi (Shih Tzu)
2017 Winnebago Travato 59K