Snellen chart


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Snellen chart

(snĕl′ən)
n.
A chart for testing visual acuity, usually consisting of letters, numbers, or pictures printed in lines of decreasing size that a patient identifies from a fixed distance.

Snellen chart

Etymology: Hermann Snellen, Dutch ophthalmologist, 1834-1908
one of several charts used in testing visual acuity. Letters, numbers, or symbols are arranged on the chart in decreasing size from top to bottom.

Snellen chart

A wall chart developed by a Dutch ophthalmologist Hermann Snellen in the 19th century, which is still used today to measure visual acuity. It consists of 11 lines of block letters of decreasing size, which are to be read at a distance of 6 metres (20 feet). Per the British Standards Institution, only letters C, D, E, F, H, K, N, P, R, U, V, and Z should be used for the testing of vision based on the letters’ equal legibility. Snellen defined standard vision as the ability to recognise a letter (“optotype”) when it forms an angle of 5 arcminutes, which is “line nine” of the letters (“optotypes”) on the chart at 6 metres.

Snellen,

Hermann, Dutch ophthalmologist, 1834-1908.
Snellen chart - used to test visual acuity.
Snellen conventional reform implant
Snellen entropion forceps
Snellen eye implant
Snellen letters
Snellen operation
Snellen reform eye
Snellen sign - bruit heard on auscultation over the eye in a patient with Graves disease.
Snellen soft contact lens
Snellen suture
Snellen test types - square black symbols employed in testing the acuity of distant vision.
Snellen vectis
References in periodicals archive ?
A reduced Snellen chart was displaced toward the subject at a constant speed of approximately 0.
While the number plate test is compulsory, the Snellen chart assessment is voluntary and requires those who fail the eye examination to notify the Driver and Vehicle Licensing Agency (DVLA).
8%) chance of a correct guess, whereas those reading a Snellen chart only have a presumed choice of 26 letters (1-in-26 or 3.
Evidence suggests that this is not the case, as the typically used Snellen chart could not sufficiently detect clinically significant levels of hypermetropia and astigmatism, when used for screening school children.
He explained the differences in Snellen and logMAR notation, how to provide a rough conversion between the two, but emphasising that there was no exact logMAR equivalent of Snellen values because of the significant design limitations of the Snellen chart.
In this situation, presenting the patient with an Amsler chart or using the letter 'T' on a Snellen chart may help to demonstrate what is meant by the term distortion to the patient.
As the sun set towards the end of the days, there would almost always be 10 to 20 patients left to see and I had to use a pen torch to light up the Snellen charts.
I have never been aware of such lines, most Snellen charts adopting a sequence of 6/18, 6/12, 6/9, 6/6, 6/5 and possibly 6/4 whereas a logMAR chart over the same range would run 6/19 [0.
The authors suggest the standardisation of VA tests by using LogMAR or Snellen charts and also the introduction of VF assessment prior to commencing driving lessons.
A full range of 27 Snellen charts is included, which gives a high level of versatility to the practitioner.