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

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.
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Snellen eye implant
Snellen letters
Snellen operation
Snellen reform eye
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Snellen soft contact lens
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Snellen test types - square black symbols employed in testing the acuity of distant vision.
Snellen vectis
References in periodicals archive ?
The average decrease of CRT at the end of three months was 380um, a decrease of 179um (p<0.001) At the end of six months of our study, the average vision of our patients had improved to 85 ETDRS letters (corresponding to a vision of 20/40 on Snellen chart).
For example, the smallest letter's size for system is 33 that is defined as Letter Category 9, so according to Snellen Chart, the smallest letter's size is 20/20 ft/m that is the 1 means the users see perfectly, and the system gives message to users "You see perfectly!".
(23) In the Hong Kong study of chronic psychiatric patients, uncorrected DVI was defined as 20/40 or worse using the Snellen chart. (5) Having calculated the frequency of uncorrected DVI in the current sample and using the same cutoff, the frequency of DVI rose to 35.7%, still lower than the 75% reported from Hong Kong.
The material resources used were: school classrooms, Illiterate E Snellen Charts, tape measures, tissues (as eye patches), class lists and feedback forms--all readily available and inexpensive.
The subject maintained focus on a 6 x 6 matrix of 20/20 letters on the clinical, near, reduced Snellen chart at 40 cm (2.5D).
I found that the amount of sphere needed to blur the Mizar-Alcor pair and the 20/20 line on the Snellen chart was almost identical.
The mean visual acuity in patients with DME after 15 years was 0.31 in the Snellen chart test and 1.26 in the Log-MAR test.
The screener used the Snellen chart since Paul seemed to have good letter recognition and he scored 20/30 in his right eye and 20/20 in his left eye.
Screening procedures, location of screening, lighting, and distance from the Snellen chart vary from school to school, and most schools do not comply with the standard.
The DVLA say this corresponds to a score of between 6/9 and 6/12 on a visual test known as the Snellen chart.
Devised in 1863, the Snellen chart is shaped like a pyramid with a large "E" at the apex with smaller and smaller lines of letters below.