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| Keywords: Snellen06.png Snellen chart svg Snellen chart ILLUSTRATIVE ONLY NOT SUITABLE FOR VISION TESTING Almost certainly public domain from en wiki This image is in the public domain because its copyright has expired in the United States and those countries with a copyright term of life of the author plus 100 years or less This particular image is not a direct reproduction of any commercially available chart It is derived from a very small reproduction that appears on p 117 of Big Secrets by William Poundstone Big Secrets is ©1983 by William Poundstone No source is given for the chart and it is not included among the many permissions acknowledgements that appear on the copyright page This image has been extensively edited by Daniel P B Smith; in particular all of the optotypes on lines 1 through 8 have been reworked Because the original Snellen chart was devised in 1862 and because I have not seen a copyright notice on Poundstone's or any other Snellen chart ”even variations ”I believe that this and all Snellen charts are in the public domain The optotypes in this chart are not precisely correct in their geometry or spacing and the chart even if enlarged to the proper size and viewed at the proper distance is not appropriate for vision testing On the principle that an encyclopedia article should be accurate this illustration presents the same letters in the same order as the traditional Snellen chart Inexpensive Snellen wall charts are sometimes used for rough evaluation as in the office of a primary-care physician In any situations where visual acuity is being evaluated carefully equipment capable of presenting a variety of letter arrangements is used Vision testing devices in motor vehicle license offices or in any situation where there is a concern that the examinee might attempt to deceive the examiner do not use this sequence of letters PD-Art Snellen charts Artworks missing infobox template | ||||
