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.
The stroke width is 1/5 of the diameter, and the gap width is the same. 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.   Researchers would be advised to use a more consistent and reliable optotype.
【初音ミク】 ランドルトの環 （Landolt C） 【オリジナル】
Miku sounds a bit different here, but it's nice =D http://d.hatena.ne.jp/kalculation/ Mp3: http://www.mediafire.com/?njz25zyezzz From NicoNicoDouga: 【初音ミク】 ランドルトの...
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Hearing was normal, but ophthalmological examination at 7 years revealed CVI with a visual acuity of 0.3 (Landolt C). He had strabismus divergence and nystagmus. Slit lamp examination and funduscopy were normal. He looked only shortly at a target and ...
Mon, 15 Sep 2014 14:39:46 -0700
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The system can measure visual acuities in the range -0.4 to 1.6 and incorporates ETDRS, British, Tumbling E, Landolt C, Kay and Lea optotypes. It also includes a low contrast acuity test, a number plate test and a range of image slides for educating ...
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.
University of Bristol
Thu, 21 Mar 2013 10:55:22 -0700
Dr Shelby Temple, now at the University of Bristol, and his team at the University of Queensland and the University of Western Australia used a modified version of the Landolt C test to discover just how fine a detail the archerfish could resolve.
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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 ...
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