"blacked" here means "bruised", Though I think the author is using this as a hyperbole to express how quickly the character brought the binoculars to his eyes. Hope this helps :)

A "black eye" means a dark bruise to the flesh and muscles around the eye. For a picture, see Wikipedia: http://en.wikipedia.org/wiki/Black_eye In English, the word "eye" is ambiguous. Usually it means the eyeball. But it can mean the eyeball plus whole area of the face that surround the eyes. As Certainly says, the passage suggests that someone hit himself in the eyes with the binoculars, so hard that he gave himself a black eye. Obviously, that is an exaggeration.