snellen chart

Main Entry: Snel·len chart
Pronunciation: 'snel-&n-
Function: noun
: the chart used in the Snellen test with black letters of various sizesagainst a white background
Snellen, Hermann (1834–1908), Dutch ophthalmologist. Snellen was director of an eye clinic at Utrecht. In 1862 he introduced a test formeasuring 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 operationbeing 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-convexplates with intervening empty space.

Snellen chart Snel·len chart (sněl'ən)
n.
A chart for testing visual acuity, usually consisting of letters, numbers, or pictures printed in lines of decreasing size which a patient is asked to read or identify at a fixed distance.