Becoming A Seeing-Eye Person

This week, I learned that my beloved little dog, Tazar*, is blind. His vision had apparently been worsening, but so slowly that his knuckle-headed owners couldn't put two and two together until too late. In the past few months we noticed him moving slowly, playing less, snarling when our other dog surprise-pounced him, getting under foot more--but it wasn't until he started walking into walls that we thought there might be anything more than Old Age.

I feel horribly guilty. How could I have missed this?

*In full, he is Tazar The Beastmaster.