Born on this date in 1836, Ferdinand Monoyer pioneered the way we measure eye sight.

Google has released a doodle to mark the 181st birthday of French ophthalmologist Ferdinand Monoyer, who created the dioptre, the unit of measurement for vision that's still used today.Born on this date in 1836, Monoyer pioneered the way we measure eye sight. He is best known for creating the Monoyer chart.The chart, which was designed more than 100 years ago, was the first eye test to use a decimal system. The chart is still used today."He developed the dioptre, the unit of measurement for vision that's still used today," said Google. "The dioptre 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 dioptre, from smallest to largest."Monoyer was known to change the font of a particular letter if it didn't suit him. He also inserted his name in the chart; reading vertically from bottom to top on each side of the chart, one can read his name.

Monoyer grew up in Lyon in France before moving to the University of Strasbourg in 1871. He eventually returned to Lyon, were he died aged 76 in 1912. His tomb is located in the Cimetière de la Guillotière in Lyon.In its tribute through its doodle, Google has used Monoyer's signatures: his name, hidden in the chart.