In 1794, Captain Horatio Nelson of the HMS Agamemnon was wounded in the face by debris thrown up by a close cannon shot during an operation off the Corsican coast, and lost the sight in his right eye.
Seven years later, at the Battle of Copenhagen, Nelson - now a Vice-Admiral - was signalled to break off the action by his commander Sir Hyde Parker, who believed the Danish fire to be too strong. Holding his telescope to his right eye, Nelson claimed "I really do not see the signal!" and ignored Parker's order to withdraw. His action was approved in retrospect, and to this day someone who intentionally ignores something is said to be "turning a blind eye".