I told my best friend about how I found out Tibby was partially blind and she said "that's why Corkscrew helps her so much." I never really thought about it, but I think that he does. Everytime she meows he always stops what he's doing to go check on her and most of the time she'll start to follow him after that. Do you think that he was able to know that she couldn't see and needs his help or is it just coincidental?