Optotypes - Ametek Reichert ClearChart2 User Manual

Installation, Features, & Functions

Optotypes

All of the optotypes contained within the ClearChart 2 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 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'. Because of this, 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 2, 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.
The tumbling 'E's and the Landolt 'C's are both presented in four positions: up, down,
left, and right.
ClearChart 2 Digital Acuity System User's Guide 13760-101 Rev. H
The Children's Shape Symbols are four shapes. As
these symbols 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 verbalized by some children than
the Children's Shape Symbols.
The Allen Symbols are only available up to size 100.
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