Tuesday’s Google Doodle honored French ophthalmologist Ferdinand Monoyer on his 181st birthday. Monoyer invented the Monoyer chart, which is used to test visual acuity.

Monoyer was born May 9, 1836 in Lyon, France. He worked as an associate professor of medical physics at the University of Strasbourg in 1871 and later worked at universities in Nancy and Lyon. He died July 11, 1912 at the age of 76 and his tomb is located in the Cimetière de la Guillotière in Lyon.

“He [Monoyer] developed the diopter, the unit of measurement for vision that's still used today. The diopter measures the distance you'd have to be from text to read it. Most notably, Monoyer devised an eye chart where every row represents a different diopter, from smallest to largest,” Google said. “Monoyer was known to change the font of a particular letter if it didn't suit him; after all, if you're going to judge a person's vision by it, that letter had better be as legible as possible!”

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The doodle is visible to users of Google in France along with several other countries in Europe, South America and Asia, Canada, Australia and New Zealand.

Following are some facts about Monoyer:

  • In 1872, Moyoner made his biggest contrition to ophthalmology, which is the branch of medicine concerning the eyeball. He developed the diopter (or dioptre in the U.K.). Diopter is the unit of measurement for the optical power of a lens.
  • Monoyer invented the eponymous chart to examine visual acuity, or how well the retina focuses.
  • The French ophthalmologist actually his full name on the chart. By taking the first letters from the second row from bottom and going up to the third row from top, the word “MONOYER” can be found. Then the last letter on the second-from-bottom row, going up to the last letter of the top row, we find his first name “FERDINAND.”
  • There is also a "DM" from where "MONOYER" ends to show his name as Monoyer DM, with DM standing for Doctor of Medicine.
  • The University of Lyon was the last university where Monoyer taught from 1877 to 1909. Prior to that, he was also a professor at the University of Strasbourg and at the University of Nancy from 1872 to 1877.
  • Before returning to Strasbourg and deciding to become an ophthalmologist, Monoyer studied at several major European universities. After his step-father Professor Victor Stoeber died, Monoyer took his place at the University of Strasbourg.
  • Monoyer's biological father was was a military doctor who died when Monoyer was just 5-years-old, according to the website of Monoyer’s Lyon villa. Monoyer’s mother, Jeanne, married Stoeber, who was a father to two daughters. The family then moved to Strasbourg.
  • Monoyer’s Lyon villa is often frequented by visitors and remains open for events.
  • After Monoyer’s death, the President of the Société Nationale de Médecine de Lyon said: “To the memory of this scholar, the Medical Society bows with respect and sadness; she has lost a friend who was also her counselor who knew to think and to reflect,” in Monoyer’s honor two months after his death.
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