title: [Look up-look down optical illusions (XIX Century)].
authors.affiliation: Servicio de Oftalmología, Hospital San Agustín de Avilés, Asturias, España.
authors.forename: J J
authors.initials: JJ
authors.lastname: Barbón
mesh_terms: D049672:History, 19th Century; D049673:History, 20th Century; D006801:Humans; D009903:Optical Illusions; D019064:Product Packaging / Q000266:history; D011584:Psychology / Q000266:history; D013030:Spain