Entitled: "Portrait of Madame Quilira. When the portrait is turned upside down there is an animal face. Cavalleri, GB. Opera nela quale uie molti Mostri, Rome 1585. A book about monsters of fact and fancy. Produced by Production Design Associates at Blair Lithograph." An optical illusion is a phenomena where one seems to see something that doesn't exist or with another perspective. It is also called visual illusion and is categorized by visually apparent images. An optical illusion is basically a visually misleading image interpreted by the brain inaccurately.