Optotypes - Ametek Reichert Clearchart 4 User Manual

Installation, Features, & Functions

Optotypes

All of the optotypes contained within the ClearChart 4 conform to the American National Standard
Institute guidelines for general purpose clinical visual acuity charts. The optotypes are constructed on
a 5 x 5 matrix such that their stroke width is one-fifth of their overall size. Letter optotypes are of Letter
Gothic typeface.
The spacing between optotypes of the same size is between one and two times the width of that size
optotype. The spacing between rows of descending size is between one and two times the height of
the larger optotype.
The letters found in the seventeen letter set have been traditionally used in many visual acuity testing
situations. This letter set consists of these letters: A B C D E F G H K L N O P T U V Z.
The eight letter set consists of these letters: C D E K N P U Z. The individual letters of this set have
been shown to be equivalent to the Landolt 'C'. Because of this, each letter is essentially equally leg-
ible to patients. Unlike the seventeen letter set, no letter is easier or harder to identify than another.
Since these letters can be presented in many combinations by the ClearChart 4, the few letters in the
letter set do not pose a problem of memorization.
ETDRS letters are the same as the Sloan letters, but are always displayed 5 per row (size permitting).
The Sloan Letter Set consists of these letters: C D H K N O R S V Z.
The tumbling 'E's and the Landolt 'C's are both presented in four positions: up, down, left, and right.
13795-101 Rev. J
The Children's Shape Symbols are four shapes. As these symbols
begin to blur, they are each perceived as circles. Available in the
ClearChart 4 only.
A second set of shapes for children consists of the following five
shapes. These symbols may be more easily recognized and verbalized
by some children than the Children's Shape Symbols. Available in the
ClearChart 4 only.
The Allen Symbols are only available up to size 100.
The LEA SYMBOLS are a circle, square, house, and apple. Available in
the ClearChart 4X only.
The LEA NUMBERS are 9, 5, 8, and 6. Available in the ClearChart 4X
only.
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