My girl has chronic tear duct issues (I thought perhaps tooth problems initially, but vet cleared that), and it recurs every two months or so, but overall it's manageable. From time to time, the others get some irritation, but that's exactly what you mentioned - some small environmental irritants that clear up in a day or two. Eye problems are a huge worry and I can only imagine how frustrated they get when their eyes are irritated.. glad to hear he's fine!