Every week is Shark Week at Cherry Creek Eye. ⁠⠀
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These Snellen eye charts, named after ophthalmologist Herman Snellen who developed the chart in 1862, are used as an initial measure of visual acuity.⁠⠀
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Consisting of symbols formally known as “opotypes,” the familiar Snellen chart is printed with eleven lines of block letters that increase in number and decrease in size with every line. The letters are read out loud from top to bottom from a distance of 20 feet away. ⁠The largest letter on an eye chart often represents an acuity of 20/200, the value that is considered “legally blind” in the US. ⁠⠀
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Did you know? The symbols on these charts are often randomized in order to deter people from cheating on the eye exams by memorizing the charts at locations like the DMV. ⁠⠀
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Cartoon by Zachary Kanin for the March 4, 2013 issue of The New Yorker.