Snellen chart

Snel·len chart 'snel-ən- n the chart used in the Snellen test with black letters of various sizes against a white background
Snellen Hermann (1834-1908)
Dutch ophthalmologist. Snellen was director of an eye clinic at Utrecht. In 1862 he introduced a test for measuring the acuteness of vision which consisted of printed letters or words in type of various sizes. He also introduced operations for entropion and ectropion and for ptosis, the latter operation being performed by shortening the aponeurosis of the levator palpebrae superioris of the upper eyelid. Snellen is additionally famous for constructing an artificial eye consisting of two concavo-convex plates with intervening empty space.

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the commonest chart used for testing sharpness of distant vision (see visual acuity). It consists of rows of capital letters, called test types, the letters of each row becoming smaller down the chart. The large letter at the top is of such a size that it can be read by a person with normal sight from a distance of 60 metres. A normally sighted person can read successive lines of letters from 36, 24, 18, 12, 9, 6, and 5 metres respectively. There is sometimes a line for 4 metres. The subject sits 6 metres from the chart and one eye is tested at a time. If he can only read down as far as the 12-metre line the visual acuity is expressed as 6/12. Normally sighted people can read the 6-metre line, i.e. normal acuity is 6/6, and many people read the 5-metre line with ease. A smaller chart on the same principle is available for testing near vision. In North America the test is done at a distance of 20 feet: 20/20 vision is the same as 6/6.
H. Snellen (1834-1908), Dutch ophthalmologist

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a standardized chart imprinted with block letters (Snellen test type) in gradually decreasing sizes, identified according to distances at which they are ordinarily visible; used in testing visual acuity. See also Snellen test type, under test type.

Medical dictionary. 2011.

Look at other dictionaries:

  • Snellen chart — A Snellen chart is an eye chart used by eye care professionals and others to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862.DescriptionThe traditional Snellen chart… …   Wikipedia

  • Snellen chart — the commonest chart used for testing sharpness of distant vision (see visual acuity). It consists of rows of capital letters, called test types, the letters of each row becoming smaller down the chart. The large letter at the top is of such a… …   The new mediacal dictionary

  • Snellen chart — noun display consisting of a printed card with letters and numbers in lines of decreasing size; used to test visual acuity • Hypernyms: ↑display, ↑presentation …   Useful english dictionary

  • Snellen chart etc. — Snel·len chart, etc. (snelґən) [Hermann Snellen, Dutch ophthalmologist, 1834–1908] see under chart, eye, sign, test, and test type …   Medical dictionary

  • Таблица Снеллена (Snellen Chart) — наиболее распространенная таблица, применяемая для проверки остроты зрения. В этой таблице содержатся строки прописных букв, называемых оптотипами (test types); размер букв уменьшается от строки к строке в направлении сверху вниз. Самые крупные… …   Медицинские термины

  • Snellen test type — block letters used in testing visual acuity, so designed that the whole letter subtends, at the appropriate distance, a visual angle usually of 5 minutes, and each component part subtends an angle of 1 minute. See also Snellen chart, under chart …   Medical dictionary

  • Snellen — noun Dutch ophthalmologist who introduced the Snellen chart to study visual acuity (1834 1908) • Syn: ↑Hermann Snellen • Instance Hypernyms: ↑ophthalmologist, ↑eye doctor, ↑oculist …   Useful english dictionary

  • Snellen test — noun a test of visual acuity using a Snellen chart • Hypernyms: ↑test, ↑trial, ↑run …   Useful english dictionary

  • Chart, Snellen's — The familiar eye chart used to measure how well you see at various distances. Snellen s chart is imprinted with block letters that line by line decrease in size, corresponding to the distance at which that line of letters is normally visible. The …   Medical dictionary

  • Snellen's chart — The familiar eye chart used to measure how well you see at various distances. Snellen s chart is imprinted with block letters that line by line decrease in size, corresponding to the distance at which that line of letters is normally visible. The …   Medical dictionary

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