The eye and brain are conspirators, and, like most conspiracies, theirs is negotiated behind closed doors, in the back room, outside of our awareness.
To ensure that our views are credible, our brain accepts what our eye sees. To ensure that our views are positive, our eye looks for what our brain wants. The conspiracy between these two servants allows us to live at the fulcrum of stark reality and comforting illusion.
Our brain accepts what the eyes see and our eye looks for whatever our brain wants.
The brain and the eye may have a contractual relationship in which the brain has agreed to believe what the eye sees, but in return the eye has agreed to look for what the brain wants.