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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 chartA 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 reform eye
Snellen sign - bruit heard on auscultation over the eye in a patient with Graves disease.
Snellen soft contact lens
Snellen test types - square black symbols employed in testing the acuity of distant vision.