from The American Heritage® Dictionary of the English Language, 4th Edition
- 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.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. display consisting of a printed card with letters and numbers in lines of decreasing size; used to test visual acuity
After Herman Snellen (1834-1908), Dutch ophthalmologist.(American Heritage® Dictionary of the English Language, Fourth Edition)