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Google doodle focuses on ophthalmologist Ferdinand Monoyer

His diopter measures how close you need to be to text to see it clearly, a development still in use today.

Google honors French ophthalmologist Ferdinand Monoyeron on his 181st birthday.

If you wear glasses to correct your vision, you have likely benefited from one of Ferdinand Monoyer's developments.

The French ophthalmologist, born 181 years ago Tuesday, developed the diopter, a unit of measure of the optical power of a lens or curved mirror. Still in use today, it measures the distance you'd have to be from text to see it clearly.

To honor Monoyer, Google has published an animated doodle that highlights the Monoyer chart -- an eye chart that tests your visual acuity. Each row of the chart represents a different diopter, from smallest to largest.

But if you read upward on both ends, starting with the second line from the bottom, Monoyer's first and last names can be seen.

If you can read it, thank an ophthalmologist.

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