View source for Landolt C

[[Image:Landolt C.svg|right|thumb|Landolt C optotypes in various sizes and orientations]]
[[Image:Golovin-Sivtsev Table.svg|thumb|right|[[Golovin-Sivtsev Table]]]]
A '''Landolt C''', also known as a '''Landolt ring''' or '''Landolt broken ring''', is an [[optotype]], i.e. a standardized symbol used for testing vision.  It was developed by the Swiss-born [[Ophthalmology|ophthalmologist]] [[Edmund Landolt]].

The Landolt C consists of a ring that has a gap, thus looking similar to the letter C. The gap can be at various positions (usually left, right, bottom, top and the 45° positions in between) and the task of the tested person is to decide on which side the gap is. The size of the C and the break are reduced until the subject makes a random rate of errors. The minimum angle of the break is judged as the visual acuity. It is generally practiced in the laboratory. <ref> "eye, human."Encyclopædia Britannica. 2008. [[Encyclopædia Britannica 2006 Ultimate Reference Suite DVD]] </ref>

The stroke width is 1/5 of the diameter, and the gap width is the same<ref>http://www.journalofvision.org/7/2/25/article.aspx</ref>. This is identical to the letter C from a [[Snellen chart]].

== See also ==
* [[Visual acuity]]
* [[E chart]]
* [[Golovin-Sivtsev Table]]

==References==
{{reflist}}

[[Category:Ophthalmology]]
[[Category:Optotypes]]

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