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Installation, Features, & Functions
Optotypes
All of the optotypes contained within the ClearChart 4P conform to the American National Standard
Institute ANSI Z80.21 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 opto-
types are of Letter Gothic typeface. The spacing between optotypes of the same size is equal to the
width of that size optotype. The spacing between rows of descending size is equal to the width 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'. Each letter is essentially equally legible 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 4P, the few letters in the letter set do not
pose a problem of memorization.
The Sloan Letter Set consists of these letters: C D H K N O R S V Z.
HOTV is an additional letter set offered in the ClearChart 4P.
The Cyrillic letters are representative of the characters used in the Golovin-Svitsev Acuity Chart:
Ш Б М Н К Ы И
The tumbling 'E's are presented in four positions: g e f h
Landolt 'C's are presented in eight positions: g f j l q t y
O Landolt C optotypes are also available.
The number selection includes 9 6 8 5 3 and are considered to be equally difficult to identify.
CHILD OPTOTYPES
"Kolt Symbols"
Children's Shape Symbols
Allen Symbols
Pigassou
J K L M N O P
Osterberg
A C D E F Q R S T V W X Z
Sheridan Gardiner
T U X H V O A
Lower Case Letters
c a x n s e r z v o
24
The Children's Shape Symbols are four shapes. As these sym-
bols begin to blur, they are each perceived as circles.
A second set of shapes for children consists of the following five
shapes. These symbols may be more easily recognized and ver-
balized by some children than the Children's Shape Symbols.
The Allen Symbols are only available up to size 100.
Set of 7 recognizable images with key card.
Set of 13 recognizable images.
Seven letter set with key card.
Set of 10 letters. Lower case letters are sometimes consid-
ered easier for children to identify.
(continued)
13785-101 Rev. F
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