Landolt C
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 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. [1]
The stroke width is 1/5 of the diameter, and the gap width is the same[2]. This is identical to the letter C from a Snellen chart.
See also
References
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no:Landolt C- ↑ "eye, human."Encyclopædia Britannica. 2008. Encyclopædia Britannica 2006 Ultimate Reference Suite DVD
- ↑ http://www.journalofvision.org/7/2/25/article.aspx
