Born 19 Feb 1834; died 18 Jan 1908 at age 73.
Dutch ophthalmologist whose Snellen Chart imprinted with traces of black letters is used for trying out visible acuity. Test kinds have been invented in 1843 via way of means of Heinrich Kuechler (1811-1873) and have been advanced via way of means of the Vienna oculist Eduard Jaeger Ritter von Jaxtthal (1818-1884) in 1854. Shortly after this Snellen invented his chart of rectangular fashioned letters. This chart quickly won popularity across the world. The Snellen fraction is a ratio, as an example 20/20 or 20/100 (metric equal 6/6, 6/30), measuring the acuity of a person’s eyesight in comparison to a popular observer with correct everyday acuity. 20/20 method he can solve 2 goal functions at 20 feet.