Google's latest Doodle marks the 181st birthday of France's most famous ophthalmologist, Ferdinand Monoyer.
Monoyer is best remembered for introducing the diopter, a unit of measurement for vision still used today, as well as the eponymous Monoyer chart used to test subjects' clarity of vision. Each row in his eye chart represents a different diopter, from smallest to largest. The diopter measures the distance a person would have to be from the text to read it.
Although his name might sound unfamiliar, there's a good chance you've read it before if you've taken an eye exam: Monoyer hid his own name within his chart, reading vertically from bottom to top along each side.
Born in Lyon, France in 1836, Monoyer studied medicine in Strasbourg and joined the faculty at the University of Nancy before eventually taking an academic position back in his hometown. He died there in 1912, aged 76.
The Monoyer Google Doodle will appear for the search engine's users in France and also a host of other countries in Europe, South America and Asia, as well as Canada, Australia and New Zealand.