What does a blind horse see?

Rio has been partially blind in his right eye since dad got him over 22 years ago.  In those intervening years, he has developed a cataract in that eye, and does not see out of it at all now.  His hearing is going, and his arthritis plagues him on the cold days.  He is getting "long in the tooth" and opts for chewing grass more often than his hay nowadays.  He patiently waited for me to get done with horse paparazzi, obligingly turning his head this way and that, probably wondering why this was necessary.  Or did he?  What is the horse equivalent to rolling your eyes in annoyance or amusement?

In looking at the pictures later that evening, I saw myself clearly reflected in Rio's eye--the one he sees with.  How do you see me, Rio? 

As I fed him one last time yesterday morning before I left, I stroked his soft fuzzy winter coat, scratched behind his ears, and told him I loved him.  He just kept eating, but I like to think that my cooing words of affection and the soft feel of my gloved hand down the side of his neck is a good memory for him, too.  Until next time, then, happy trails to you, Rio.