In 1450, the Duke of Urbino, Federico da Montefeltro, became monocular after losing vision in his right eye following a jousting accident. In order to improve the peripheral vision of his left eye, he had surgeons cut off the bridge of his nose. In Piero della Francesca’s 1472 portrait, the Duke is depicted in profile, so we can see that an equilateral triangle of flesh and bone has been chopped from what must have been an elegant aquiline beak.