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Landolt C optotypes in various sizes and orientations

A Landolt C, also known as a Japanese Vision Test, 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 its gap are reduced until the subject makes a specified rate of errors. The minimum perceivable angle of the gap is taken as measure of the visual acuity. It is generally practised 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. The Landolt C is the standard optotype for acuity measurement in most European countries. It was standardized, together with measurement procedures, by the German DIN, as DIN 58220 (now EN ISO 8596).

Although accepted as a 'gold standard' this optotype has its own inherent problems, possibly due to higher brain function where the gap will appear closed near the limit of resolution, especially when the gap is at the 6 o'clock position. This is not due to the structure of the cornea or lens, nor is it due to astigmatic errors. [3] [4]

See also[edit]

References[edit]

  1. ^ "eye, human."Encyclopædia Britannica. 2008. Encyclopædia Britannica 2006 Ultimate Reference Suite DVD
  2. ^ Danilova MV, Bondarko VM (2007). "Foveal contour interactions and crowding effects at the resolution limit of the visual system". J Vis 7 (2): 25.1–18. doi:10.1167/7.2.25. PMC 2652120. PMID 18217840. 
  3. ^ The visual resolution of Landolt-C optotypes in human subjects depends on their orientation: the ’gap-down‘ effect Michael Schraufa, , , Claudia Sternb Neuroscience Letters 2001
  4. ^ The Effects of Optical Defocus on the Legibility of the Tumbling-E and Landolt-C REICH, LEWIS N. OD, PhD, FAAO; EKABUTR, MICHELE Optometry & Vision Science:June 2002

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Landolt_C — Please support Wikipedia.
This page uses Creative Commons Licensed content from Wikipedia. A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia.

26 news items

Gizmodo

Gizmodo
Thu, 24 Sep 2015 15:00:15 -0700

My graphic design students love to design posters using the classic eye chart composition, and they frequently ask “What typeface should I use for this?” Not having a definitive answer has always been frustrating, so I decided to investigate to find ...

University of Bristol

University of Bristol
Thu, 21 Mar 2013 10:55:22 -0700

Dr Temple said: "This modified Landolt C test works because the only difference between the two letters is the gap in the 'C' so in order to tell the difference and spit at the right target to get their reward the fish must be able to resolve the gap ...

Medscape

Medscape
Mon, 15 Sep 2014 14:33:45 -0700

LONDON — The Alpha IMS retinal prosthesis (Retina Implant AG, Germany) gives a modicum of useful vision to some patients with severe visual loss from retinitis pigmentosa, a new study shows. "Electronic implants are the only possibility for patients ...

ModernMedicine

ModernMedicine
Wed, 15 Jan 2014 14:09:56 -0800

... reported that after implantation of the device light perception was restored in 8 of the 9 patients, light localization in 7, motion detection in 5, grating acuity measurement in 6 up to 3.3 cycles per degree, and visual acuity measurement with ...

Le Temps

Le Temps
Fri, 25 Sep 2015 10:22:55 -0700

«Le score électoral du PBD ne joue aucun rôle pour l'avenir d'Eveline Widmer-Schlumpf et la candidature de Jacques Marti n'est pas un geste de défiance contre Martin Landolt. C'est un problème de monoculture politique propre à Glaris et qu'il faut ...

Global Times

Global Times
Thu, 14 Nov 2013 02:23:15 -0800

He said one reason for this was because the test set by the Civil Aviation Administration of China (CAAC) uses the Landolt C eye chart which is more difficult than the E chart school students are familiar with. Students who pass the first interview and ...

PR Web (press release)

PR Web (press release)
Wed, 16 Jul 2014 02:56:15 -0700

The LEA symbols tests are the only tests that have been calibrated against the standardized Landolt C vision test symbol. The Landolt C is an optotype that is used throughout most of the world as the standardized symbol for measuring visual acuity.
 
ScienceBlog.com (blog)
Wed, 16 May 2012 08:19:00 -0700

A method developed at the Hebrew University of Jerusalem for training blind persons to “see” through the use of a sensory substitution device (SSD) has enabled those using the system to actually “read” an eye chart with letter sizes smaller than those ...
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