Focus is an interesting thing.
Optical illusions show us that we only “see” what our brain interprets out of the incoming data. (Was that dress white and gold or black and blue?)
The human brain does a great job of making patterns out of incomplete information and trying to “see” what might or might not be there. (Is that a face in the three-prong electrical outlet?)
“Out of focus” data coming from the eye to the brain is no less valid than “in focus” data, but the brain has so much more trouble making patterns out of it.
Without patterns, which we blame on the focus, we are functionally blind with our eyes wide open. (Take off your glasses or contacts if you wear them, or put some on if you don’t.)
We are odd, imperfect creatures.