Snellen chart

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Snel·len chart

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.

[After Herman Snellen (1834-1908), Dutch ophthalmologist.]
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Noun1.Snellen chart - display consisting of a printed card with letters and numbers in lines of decreasing size; used to test visual acuity
display, presentation - a visual representation of something
References in periodicals archive ?
Subsequently, data for patients with an initial Snellen fraction of 20/20 or better were deleted, and the remaining pooled data for the two eyes were compared, pre- and post-treatment, with the Wilcoxon signed rank test.
However scientifically sound logMAR may be, it is not intuitive in the way that the Snellen fraction is.
A viewer whose visual acuity is indicated by the Snellen fraction 20/X means the viewer can see at 20 feet what a viewer with average eyesight can see at X feet.