One thing I'd suggest is fatty acids. I was diag. w/ dry eye about a year ago, to the point my vision was affected and it was scary. One of THE things recommended for humans is fatty acids - fish oil alone for me did not help. I found one at Target w/ fish, flax, and borage and - it REALLY helped.
I use fatty acids for my boys (for other reasons) and I really like Ark Naturals Royal Coat bc it contains the fish oil fatty acids (EPA/DHA), but also contains GLA and LA from the borage oil - + it has vit a/d/e - and E must be given when giving fish oils. So, I'd recommend giving it a try for dry eye, it may help.