I remember reading an article in a cat magazine about 5 years ago that talked about a person who was rescuing feral cats. She specifically mentioned that she never looks the cat directly in the eye as that would be too challenging but instead would blink (or squint) at them. She said it is a non-challenging way for cats to look at one another and to communicate an "I am friendly" message.

My husband and I call it "sleepy eyes" and communicate with all of our cats that way. Often purring, head butts and kisses accompany it.