|
||||||||||||||||
|
||||||||||||||||
|
||||||||||||||||
|
| ||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 14
CHAPTER 3
COLOR VISION TESTS
HISTORICAL INTRODUCTION
One of the earliest methods used to test color vision was to compare
the individual's color naming of everyday objects with that of a normal
person. This was the method employed by Turberville (1684} and by
several subsequent investigators. Dalton (1798) gave a detailed
description of his own perceptions and those of his brother (both
protanopes) and of some 20 other persons.
The next advance in testing was made by Seebeck (1837), who
required the observer to choose from a wide range of colored samples
those that matched or most closely resembled a selected test sample.
The task was performed by inspection and without color naming. Variants
of this test were devised by Holmgren (1877) using skeins of wool; by
Abney (1906), Oliver (1902), and Edridge-Green (1920) using small beads
or pellets; and by Fridenberg {1903) using small square pieces of
colored cardboard. Molmgren's wool test is based on the principles of
Helmholtz ' s theory of color vision. Belmholtz (1866) had tentatively
proposed that color blindness could manifest itself in three forme--red,
green, or violet blindness--depending on the missing type of color
receptor (one for red, one for green, and one for violet). Although
this position was subsequently abandoned by Helmholtz as erroneous,
Hol~gren adhered to it and selected three standard wool skeins (red,
green, and purple) specifically to detect the three proposed types of
color blindness. As a result, the Mo~mgren test is based on an
erroneous and misleading set of color blindness categories and an
unwise choice of test and match skeins.
Pseudoisochromatic plates were f irst introduced by Stilling
(18733. The success of tests of this kind depends on the inability of
color-defective observers to discriminate between certain colors. A
symbol (number, letter, or geometric figure} composed of colored spots
is set in a background of differently colored spots. The most
frequently encountered design involves colors chosen so that the symbol
is not seen by the color-defective observer {pseudo-isochromatic ,
falsely appearing of the same color).
of this k ind of test.
Lord Rayleigh {1881 ), using his color mixing apparatus , which
employed narrow spectral bands of red and green to match yellow,
There are many modern variants
~4
OCR for page 15
15
discovered that a few observers made matches that were very different
from those made by the majority of other observers. It is agreed that
the anomaloscope is the only clinical method capable of classifying the
color defects by their presumed genetic entities. The spectral colors
used by Rayleigh were incorporated by Nagel (1899, 1900, 1907) in his
anomaloscope.
In the lantern test, which was introduced by Williams (1903),
colored signal lights were to be named by the observer. The advantage
of such a test when applied vocationally is that the task can be made
to simulate the real-life situation quite closely. Variants of the
lantern test are still used today for testing transport workers and
members of the armed forces of many countries.
Arrangement tests require the observer to arrange a set of colored
samples in sequence. This kind of test was developed by Pierce (1934)
and was first used in the National Institute of Industrial Psychology
in London. All previously devised color vision tests were designed to
separate color-defective observers from normal observers but did not
indicate the wide range of color ability and aptitude that exists among
normal observers. Pierce 's solution was to develop a surface color
test in which color ability could be measured by an observer's skill in
arranging and matching color series. Applicants had two tasks to
perform: to grade and then to match a series of nitrocellulose lacquer
discs that varied in saturation and hue. In the grading test, 16 discs
of one hue were presented in random order to the observer, who had to
arrange them in a saturation series. In the matching test, prearranged
series of discs of one color were presented to the observer who then
had to select their match from a duplicate group of discs. Modern
variants of arrangement tests involving hue discrimination were devised
by Farnsworth (1943) in the FM 100-hue and the Panel D-15 tests. The
Inter-Society Color Council of America (ISCC) employed colored plastics
in the ISCC Color Aptitude Test, which involves saturation discrimina-
tion. Most recently, Lanthony (1974b, 1975b) has developed two
arrangement tests (the Lanthony Desaturated Panel D-15 and the Lanthony
New Color Test) for use in diagnosing acquired color vision defects.
GENERAL DESCRIPTION OF TYPES OF COLOR VISION TESTS
Anomaloscopes
Anomaloscopes are optical instruments in which the observer must
manipulate stimulus control knobs to match two colored fields in color
and brightness. The anomaloscope is the standard instrument for the
diagnosis of color vision defects. When supplemented by information
from other color vision tests, the results provided by this instrument
permit the accurate classification of all color deficiencies. A
variety of instruments were available in the past, but currently the
Nagel, the Neitz, and the Pickford-Nicolson anomaloscopes are
commercially available in the United States.
OCR for page 16
16
Of all of the color vision tests described here, anomaloscopes are
the most difficult to use. Extensive training of examiners is
necessary if anomaloscopes are to be used validly and efficiently;
hence, these instruments are most often found in research settings.
However, when used by a skilled examiner, the anomaloscope has
advantages as a diagnostic instrument that far outweigh any
inconveniences in training.
Plate Tests
In a plate test, the observer must identify a colored symbol embedded
in a background (most pseudoisochromatic plates); identify which of
four colors is most similar to a standard color, (City University
Test); or identify which circle matches a gray rectangle (Sloan
Achromatopsia Test).
There are many types of pseudoisochromatic tests (e.g., American
Optical Hardy-Rand-Rittler, Ishihara, Dvorine, Tokyo Medical College).
All provide efficient screening {90 to 951) of congenital red-green
defects. Basically these tests consist of a series of cards on which
colored dots of discs of various sizes are printed to form a multi-
colored figure against a multicolored background. The figure is some
easily identifiable letter, arable numeral, or geometric configuration
(e.g., a circle, triangle, or cross). The only systematic difference
between the figure and background dots is in color: the figure is
composed of dots of one or more colors, and the background is composed
of dots of different color or colors. Variations in the size, light-
ness, and saturation of the dots may be employed so that identification
of the intended figure by cues other than hue is less likely. Observers
with normal color vision can detect the hue difference between figure
and background and consequently can easily read the figures, but
observers with defective color vision may fail to distinguish between
figure and background colors and hence fail to read the figures. In
this sense the colors of the plates appear isochroma~ic only to the
defective observer.
Hardy, Rand, and Rittler (1945) characterized four types of pseudo-
isochromatic design: the vanishing design, the qualitatively diagnostic
plate, the transformation plate, and the hidden defect design. The
vanishing design contains a figure that is easily read by the normal
trichromat but not by the color-defective observer. The qualitatively
diagnostic plate is a vanishing plate that permits the differentiation
of a proton from a deutan observer. In the transformation plate, two
figures are embedded in the background: one figure with the appropriate
color and lightness contrast to be read by the normal trichromat, and
the other with the appropriate color and lightness contrast to be read
by the color defective. In the hidden digit design, the plate is a
vanishing plate for normal trichromats, but the figure is seen by the
color-defective observer. Lakowski {1965b, 1966, 1969, 1976) has
analyzed the calorimetric properties of several of the pseudoiso-
chromatic plate tests.
OCR for page 17
17
The City University Test was designed to detect color confusions
(i.e., colors that appear quite different to the normal observer but
appear similar to the defective observer), and the Sloan Achromatopsia
Test was designed to detect achromatopsia (i.e., the inability to
differentiate any of the rainbow hues or their intermediaries other
than on the basis of lightness).
There are certain advantages in the use of plate tests. They are
rapidly and easily administered by inexperienced personnel; they are
readily available; they are relatively inexpensive; and they can be
used on naive subjects, illiterates, and children. There are, however,
certain disadvantages. First, the spectral quality of the light source
illuminating the plates affects the reading of the figures; the plates
must be exhibited under the standard viewing conditions for which they
were designed. Second, the success of the plates depends mainly on the
careful selection of confusion colors. Often, for technical reasons,
the best confusion colors for diagnostic purposes are not available.
Third, even when a set of colors is chosen, individual variation in the
eye lens and in coloration of the back of the eye means that a single
choice of colors will not be optimal for all observers. Finally, no
accurate scoring criteria for classifying defects on the basis of test
performance are available; the number of errors on pseudoisochromatic
tests tells us little about the type or extent of a color vision defect.
Pseudoisochromatic tests should be used primarily as screening tests
to divide people into normal and color-defective populations; their
diagnostic value is limited. Caution should be used in extracting more
detailed information about color discrimination from them. At present
it is always better to look on information from pseudoisochromtic plate
tests as providing a probable but not certain diagnosis.
Arrangement Tests
In arrangement tests, the observer is required to arrange color samples
by similarity in a sequential color series. Usually the colors are
mounted in caps, which are numbered on the back and can be moved about
freely during performance. Arrangement tests may be designed for
evaluation of fine hue discrimination (FM 100-hue test); for evaluation
of color confusion (Farnsworth Panel D-IS, Lanthony Desaturated Panel,
Lanthony New Color Test); for evaluation of neutral zones or colors
seen as gray (Lanthony New Color Test); and for evaluation of saturation
discrimination (Sahlgren Saturation Test, ISCC Color Aptitude Test).
Arrangement tests are easy to administer and can be used with naive
subjects. Such tests require manual dexterity, patience, concentration,
and the understanding of abstract ordering. Hence, they are less
suitable for young children. The Farnsworth Panel D-15 and the Lanthony
Desaturated Panel provide rapid tests of gross color confusions but are
not designed for fine color screening. The FM 100-hue test is more
time-consuming, but it is acknowledged to be a sensitive indicator of
aptitude for hue discrimination. Both the Panel D-15 and the 100-hue
tests differentiate among protan, deutan, and tritan defects by the
axes along which confusions are made. The ISCC test takes 45 to 90
OCR for page 18
18
minutes to complete and does not provide specific information about
color defects.
Disadvantages of arrangement tests include the fact that some
manual dexterity is required. For tests using colored papers, the
observer should wear a glove to avoid soiling the colored pigments.
The specified illuminant must be used.
Lantern Tests
Lantern tests were designed as practical means for measuring the
ability of seamen, railway personnel, and airline pilots to identify
and discriminate navigational aids and signals. Accordingly these
tests emphasize correct color recognition as the important testing
variable. The design of lantern tests is straightforward, necessitating
neither the construction of complex optical systems (as do anomalo-
scopes) nor the development of complicated color printing procedures
(as for pseudoisocbromatic plate tests). Lantern tests simply require
that a system be developed for presenting colored lights (duplicating
signal lights) to the observer for identification. Several different
models of lanterns are available: Giles-Archer, Edridge-Green,
Martins, Sloan Color Threshold Tester, and Farnsworth Lantern.
Lantern tests are easy to administer. Their value lies in their
simulation of the working condition. Lantern tests do not specifically
screen for color defect, although it is expected that color-defective
observers will not perform as well as observers with normal color
vision.
HOW TO EVALUATE A COLOR TEST
Reliability and Validity
Evaluation of a new color test requires knowledge of its reliability
and its validity. The term reliability refers to whether the test
measures the same property on each occasion. Reliability is assessed
by administering the tent on two separate occasions. Statistical
procedures are then used to compare the two sets of results. The term
validity refers to whether the test measures what it claims to measure.
For a test designed to screen or detect color defect, the results may
be compared to another standard test. The Nagel Model T anomaloscope
is considered a standard test of red-green color vision.
In comparing two tests, a statistical measure of agreement is
necessary. An appropriate measure is the K statistic developed by
Cohen (described by Bishop et al., 19751. Normally, K will be between
O and 1. A value of zero indicates that agreement is only at the~level
of chance; a value of 1 indicates perfect agreement. A negative K may
occur, although it is unlikely to be found with well-known tests of
color vision, since such a value indicates that agreement is below
chance. The statistic ~ may be interpreted as the number of actual
agreements divided by the total possible number of agreements, adjusted
r
OCR for page 19
19
to exclude the number of agreements expected by chance alone.
Specif ically
K =
Percentage of observations
for which there is agreement
Percentage of agreements
expected by change alone
1009
Percentage of agreements
expected by chance alone
For example, a computation formula for a two-by-two table would be as
follows:
Test 1
Pass Fail Total
Pass
a b a + b
Test 2 Fail
c d c + d
Total
a + c b + d N
R ~ (a + d) - (a + c){a + b) + (b ~ d)(c + d)
N
N
N - (a + c) (a + b) + (b + d)(c ~ d)
N N
A conditional K is computed in the same way, except that the expected
agreements are calculated only for a particular row or column {on which
the statistic is conditional). Hypothesis tests have been developed
for K (Bishop et al., 19757.
Specific Procedures for Calculating Different Types of Tests
Plate Tests
The appropriate procedure is to compare K coefficients for reliability
and validity. Evaluation of reliability should compare test and retest
data; evaluation of validity should compare plate test data and
anomaloscope data. In many cases, plate tests have been compared with
other plate tests of known high validity. This procedure is less
desirable than comparison with a standard anomaloscope.
e
OCR for page 20
20
Arrangement Tests
Reliability and validity of arrangement tests with pass/fail criteria
can be evaluated by the K coefficient. For the FM 100-hue test,
calculation of K coefficients is possible only for comparisons of
classification data. Other standard statistical procedures, including
analyses of variance, may be used to compare error scores.
Anomaloscopes
If appropriate technique is used, reliability of anomaloscope data
should be high. If necessary, reliability of match midpoint or
matching range can be evaluated by means of a scatter plot. Instrument
values for the anomaloscope on initial testing are plotted against
values obtained on retest. Since match midpoints are usually
distributed normally and symmetrically (Lakowski, 1971), a correlation
coefficient can be computed.
In order to evaluate the validity of new anomaloscopes, the
diagnostic categories obtained from the new anomaloscope (i.e., P. PA,
EPA, D, DA, EDA; see pages 9-llJ should be compared with those from the
Nagel anomaloscope, which is accepted as a standard instrument, and
the K coefficient should be calculated. It is appropriate to use
scatter-plot and correlational analyses to compare match midpoints and
matching ranges of two anomaloscopes that have identical mixture
primaries and test wavelengths. In order to compensate for scale
differences, however, the data must either be converted to the
comparable scale units devised by Willis and Farnsworth (1952) or
expressed in anomalous quotients. (The anomalous quotient expresses an
individual observer's match relative to the mean of many observers.
See Existing Tests,. in this chapter.} It is not appropriate to
compare match midpoints, matching ranges, or anomalous quotients of two
anomaloscopes that have different mixture primaries or test wavelengths.
Lantern Tests
The reliability of lantern tests may be assessed by K coefficients.
Since lantern tests are field tests, the assessment of validity is
virtually impossible. Lantern tests, however, may be compared with
other color vision tests to check their agreement.
ILLUMINANTS
The majority of the plate and arrangement tests (see General
Description,. in this chapter) were designed and standardized either
for natural daylight or for an artificial illuminant called CIE
(Commission Internationale d'Eclairage) Standard Illuminant C. Standard
Illuminant C appears slightly bluish white. Natural daylight refers to
afternoon northern sky light in the northern hemisphere. Standard
OCR for page 21
21
Illuminant C approximates the average spectral distribution of natural
daylight. However, the level of illuminance and spectral composition
of natural daylight are not as constant as can be obtained with an
artificial illuminant. Standard Illuminant C can be realized physically
by an incandescent tungsten lamp of appropriate wattage (called Standard
Illuminant A) in conjunction with a specified liquid filter that changes
the spectral distribution to that of Standard Illuminant C. There are
several glass filters that closely approximate the liquid filter.
To demonstrate the importance of using the correct illuminant, a
number of investigators showed that if ordinary unfiltered tungsten
lamps (which appear yellower than Standard Illuminant C) are used,
deutan subjects make fewer errors in pseudoisochromatic plate tests,
including the Ishihara, American Optical Co., and AO H-R-R tests (Reed,
1944; Hardy et al., 1946; yolk and Fry, 1947; Farnsworth, Reed, and
Shilling, 1948; Schmidt, 1952; Katavisto, 1961; and Higgins et al.,
1978~.* Therefore, deuteranomalous observers {deutans) may pass a
screening test that was administered under the wrong illuminant. With
the wrong illuminant, deutans may also make fewer errors in an arrange-
ment test, such as the FM 1oo-hue test or the Farnsworth Panel D-15.
In addition, protans may show rotation of the error axis. Extreme
protanomalous trichromats and protanopes may even show a deutan
pirofile (Higgins et al., 1978~. Thus, unfiltered tungsten lamps
cannot be used as illuminants for these tests, since those lamps will
not give correct results. Ordinary window light is too variable in
both illuminance level and spectral composition to be an adequate
source for color vision testing. The use of fluorescent tubes in color
testing has been investigated, with variable results (Rowland, 1943;
Katavisto, 19617. Ordinary commercially available fluorescent tubes
are not generally appropr late for testing color vision .
In recent years, high-quality fluorescent lamps have been developed
especially for use in color comparison work. Richards and colleagues
(1971) compared two lamps manufactured in the United States--the GE
Chroma 70 and the Verd-A-Ray Cr iticolor Fluorescent--with the Macbeth
Easel Lamp, which was designed for use with screening plate tests.
While the lamps gave similar screening data on the AO B-R-R and Panel
D-15 tests, and similar total error scores on the FM 100-hue and ISCC
tests, the classification data varied among the three illuminants. The
authors suggested some caution in using these fluorescents for
evaluation of color vision.
Very few tests specify the necessary level of illumination. The
AO H-R-R should be viewed under 100 to 650 lux (Hardy et al., 1954a);
the Farnsworth-Munsell 100-hue test and the Farnsworth Panel D-15
should be viewed under 270 lux. The City University Test is specified
*The Freeman Illuminant Stable Color Vision Test was designed as
rapid-screening testing that would be valid under all illuminants
(Freeman, 1948; Freeman and Zaccaria, 1948~. The test did not prove to
be a successful screening test (Farnsworth et al., undated); it is no
longer in production.
OCR for page 22
22
for 600 lux. The majority of researchers would consider 100 lux to be
a minimal level for screening purposes. Screening-test results are not
affected by changes in level of illumination between approximately 100
and 1000 lux.
If the aim of research is evaluation of color discrimination, an
illuminant that provides 2000 lux is preferable. Error scores on the
FM-100 hue test vary with the level of illumination. Above 100 lux,
Increased zilum~nat~on can improve the error scores of observers whose
chromatic discrimination was below average at a lower level. These
data make it clear that age norms are valid only at the level of
illumination specified. The Verriest (1963) age norms (Table 3-2) are
for 100 lux. Lower error scores would be expected with 2000 lux
illumination. With reduction in illumination below 100 lux, error
scores increase, showing first a blue-yellow confusion axis at an
illumination of 15 lux, and, f inally, a scotopic axis as illumination
is reduced to a range of 0.04 to 0.20 lux.
Table 3-1 lists, describes, and names the supplier of some
illuminants that are commercially available in the United States. The
table includes three illuminants that use a tungsten source with
filters, five fluorescent sources, and one xenon source. For some of
the illuminants, correlated color temperature, color-rendering index,
and approximate level of illumination are shown. The correlated color
temperature specifies the spectral energy distribution of the source;
Standard Illuminant C has a correlated color temperature of 6774 K.
The color-rendering index expresses how closely a test source can
reproduce color in comparison with a standard source. An index of 100
is perfect rendition tWyazecki and Stiles, 19671.
The Macbeth Easel Lamp, designed for use with screening-plate
tests, is a widely used illuminant in the United States. The lamp is
mounted in a stand which allows source, plate test, and observer to be
in correct spatial relationship. The daylight filters for the lamp
vary slightly but are close to Standard Illuminant C. The Macbeth
Daylight Executive consists of a metal light box that provides diffuse
illumination. The various color tests placed in the box are viewed in
correct spatial relationship to the observer. The color test glasses
(Pokorny et al., 1977; Pokorny et al., 1978) are a pair of
color-correcting glasses designed to be used with an ordinary 200-watt
light bulb.
The color-rendering indices for the fluorescent lamps listed in
Table 3-1 are almost as good as those for the filtered tungsten sources
or for the one filtered xenon source. It should be noted that
conventional commercially available fluorescent lamps do not have
color-rendering properties equivalent to those of the special lamps
listed in Table 3-1. For example, a conventional commercially
available ~daylight. fluorescent lamp has a correlated color
temperature of 6673 K but a color-rendering index of only 76.
The observer, test material, and illuminant should be arranged to
allow a comfortable position during test performance. The observer
should be seated at a desk or table. The test mater ial should be
approximately perpendicular to the observer's line of regard to avoid
g fare or gloss. The illuminant should be mounted above the test
1
OCR for page 23
23
TABLE 3-1 Some Commercially Available Illuminants*
Name Correlated Color-
and/or Color Render ing
Description Supplier Temperature Index Illumination
Tungsten Sources with Filters
Macbeth Easel Lamp Macbeth, U. S. c . 5500 K - c. 100 lux
(with 100 W tungsten (value marked
lamp and daylight f liter on the f liter )
Macbeth Daylight Executive - 1850 lux
Color test glasses House of 6800 K 96 385
(used with 200 W Vision,
tungsten source ) U. ~ .
Xenon Sources
150 W Xenon Arc Macbeth, U. S. . 6580 K 97
XBOF 6500 with
one f liter
Fluorescent Source s
.
440 Luminaire (fluorescent) Macbeth, U.S. 6720 K 91
NL 6500
Fluorescent Macbeth Macbeth, U.S. 6710 K 90
NL 6500 ~ F40T12
Chroma 75 General 7500 94
F15T8 C75 Electr ic
U.S.
Criticolor Fluorescent Verd-A-Ray 5700 K 91
F 1 sT8/CC U. S. .
Ver flux Dayl ight Ver flux, U. S. . 6200 K 94
F15T8 VLX
*Data supplied by J.D. Moreland.
material and adjusted to provide even and direct illumination. The
distance of the illuminant from the material determines the level of
illuminance and the area of illumination. Plate tests should be
presented at a distance of about 75 cm. Arrangement tests are
presented at a distance comfortable for manipulation (about 50 cm).
OCR for page 24
24
TABLE 3-2 Error Scores on FM 100-hue Test According to Age*
Age Mean Standard 9 s
Group N Score Deviation Lowest Highest Percent
10-14 49 83.1 38.2
15-19 56 51.5 28.6
20-24 94 36.3 31.2
25-29 51 47.4 29.4
30-34 33 54.7 35.2
35-39 37 56.8 34.2
40-44 32 62.4 28.5
16 194 160
8 124 100
4 162 74
4 116 92
8 176 106
8 156 120
16 178 134
45-49 30 90.4 39.3 36 184 144
50-54 38 71.5 31.3
55-59 31 96.7 41.9
60-64 29 87.9 35.0
24 140 1S4
12 176 164
28 1S2 174
*Data from Verriest (1963~.
EXISTING TESTS: AVAILABILITY, PRACTICALITY, AND PPOCEDtJRES
Anomaloscopes
Nagel Model T
Made by Schmidt and Haensch, Berlin, Germany
Available in Canada from Imperial Optical Company, Ltd.
Available in United States from Alfred P. Poll, 40 West 55th
Street, New York, NY 10019
Nagel Model II is out of production.
OCR for page 70
70
circle from the reference cap. The procedure is the same as that for
the Farnsworth Panel D-15. Subjects with normal color vision usually
make only one or two minor errors. Occasionally a single line crossing
the circle may occur when the observer reverses part of the series.
Simple anomalous trichromats make some minor and major errors.
Dichromats and extreme anomalous trichromats make multiple (6 to 10)
crossovers forming a nearly parallel series of lines. The axes of
these crossover lines are the same as those found on the Farnsworth
Panel D-15.
Maintenance. Requirements are the same as those for the Farnsworth
Panel D-15.
Calibration. The caps use Munsell colors specified by Lanthony
(1974b). CIE specification of the caps is available. No calibration
is required by the user. Illuminant C or a close approximation must be
used.
Reliabilitv. We have not located test-retest data in our research.
Validity. Verriest and Calowaerts (1978) noted that 82 percent of
observers with congenital red-green color defects failed the Lanthony
Desaturated Panel, including 98 percent of the dichromats and 70
percent of the anomalous trichromats. Qualitative classification was
excellent for dichromats, but only 78 percent of the anomalous
trichromats were correctly classified. Insufficient data were given to
calculate K. Pinckers and colleagues (1976) and Lagerlof (1978) have
discussed the use of the Lanthony Desaturated Panel in acquired color
vision defects.
Other Remarks. This is a new test designed specifically to detect
mild discrimination loss in congenital and acquired color defect
(Perdriel et al., 1975~. It is not a screening test and should not be
used for this purpose. The test may be used to classify the severity
of discr imitation loss in congenital red-green color defects and the
progression of defect (recovery or deterioration) in acquired color
vision defects.
The Lanthonv New Color Tes
-
New Color Test de Lanthony Selon Munsell, Luneau Ophtalmologie,
Paris, 19
70 Munsell colors
Available from House of Vision, 137 N. Wabash, Chicago, IL 60602
General DescriDtion. The New Color Test was designed specifically
for use in acquired color vision defects. The test allows determination
of neutral zones (colors that are confused with gray} and tests
chromatic discriminative ability at each of four saturation levels.
OCR for page 71
71
The New Color Test includes four boxes, each with 15 colored caps.
The 15 hues are the same in the four boxes and are designated by their
initials (in French). The hues represent approximately equal steps in
the color circle. All the caps have equal lightness. The boxes differ
in saturation: the first box (high saturation) has Munsell chrome 8
(Box 8/6~; the second (medium saturation) has Munsell chrome 6 (Box
6/6~; the third (medium saturation) has Munsell chrome 4 (Box 4/6); and
the fourth (low saturation) has Munsell chrome 2 (Box 2/6~. In addition
to these 60 colored caps, the test includes 10 gray caps of varying
lightness, with values increasing from 4 to 8 in steps of 0.~; there
are two caps at value 6. They are designated by Munsell nomenclature,
N4 to N8. The caps subtend 1.5° at 50 cm. An instruction manual and
scoring sheets are provided. Additional scoring sheets are available.
The test is presented at a comfortable distance using Standard
Illuminant C providing 250 lux.
Administration. The test is performed in two phases: a separation
phase followed by a classification phase. In the separation phase, the
15 colored caps of the box at chrome 8 (Box 8/6) and the 10 gray caps
are mixed together and are presented to the observer, who must separate
the caps into two groups: a group of caps that appear gray and a group
of caps that appear colored. In the classification phase, the observer
first arranges the caps in the group that appears gray in a row ranging
from dark to bright. This part of the test allows determination of
position in the gray scale of the colored caps that appear gray to the
observer. Second, the observer arranges the caps that appear colored
according to their natural color order. This procedure differs from
that used in the Farnsworth Panel D-15 in that the observer chooses the
starting cap; there is no fixed starting cap. Furthermore, since the
classification phase follows the separation phase, there may not always
be 15 colored caps remaining, although there may be some gray caps In
that group. This procedure is repeated for Boxes 6/6, 4/6, and 2/6.
Scoring. There are two scoring sheets, one for each phase of the
test. Separation phase: The errors are plotted on a circular diagram
on which hue is represented on the circumference and chrome is
represented as a radial distance from the center. The diagram includes
four concentric rings (4 chrome), and each ring contains 15 compartments
(15 hues). The results of the test are expressed by penciling in the
hue compartments that correspond to the colored caps wrongly placed
among the grays. Classif ication phase: The positions in the gray
scale of those colored caps grouped among the grays are indicated on a
diagram with hue on the abscissa and the value on the ordinate. For
each colored cap that is wrongly placed among the grays, a circle is
drawn at its position on the gray scale. Finally the order of the
colored caps is recorded on a diagram analogous to that of the Panel
D-15 but with four concentric rings. At each chrome level, a line is
drawn connecting caps placed adjacent to one another.
Maintenance. Requirements are the same as those for the Farnsworth
Panel D-15.
r
OCR for page 72
72
Calibration. The caps use Munsell colors specif fed by Lanthony
( 1975b) . CIE specif ication is also available. No calibration is
required by the user. Illuminant C or a close approximation must be
used.
Reliability. No test-retest data were located during the course of
our research.
Validity. A number of authors are evaluating this test for
acquired color vision defects (Lanthony, 1975a, 1978; Pinckers, 1978a,
1978b, 1979~.
Other Remarks. This test is designed specifically for acquired
color vision defects (Lanthony, 1974a). The separation phase allows
determination of neutral zones according to the colored caps confused
with the grays at four saturation levels. The classification phase
allows determination of relative luminosity according to the position
of colored caps in the gray scale, and of chromatic discrimination
according to the ar rangement of the colored caps.
Sahlgren's Saturation Test
12 caps in a case
Available from Visumetrics, Hallstenhagen 26, S-421 56 V Frolunda,
Sweden
General DescriDtion. Sahlgren's Saturation Test was designed to
evaluate the loss in saturation discrimination that is characteristic
of acquired color vision defects. The 12 caps include five greenish
blue and five bluish purple samples of varying saturation plus two gray
caps. The colors are set in plastic caps and subtend 3.45° at 30 cm.
They are labeled on the back with their color and a saturation score of
zero for the gray caps and of 5, 10, 20, 30, and 40 for the two sets of
colored caps . The samples were taken f rom the Natural Color System,
which is the official Swedish color standard.
Administration. The caps are arranged in random order on the upper
lid of the box. The test is presented using an approximation to
Illuminant C that provides 400 lux. The observer is instructed to
transfer all caps that appear bluish purple or greenish blue to the
lower lid, leaving only the caps that appear gray in the upper lid.
The test takes less than two minutes.
Scoring. The test is scored by summing the saturation scores
printed on the back of the caps. A score of 10 is considered the upper
limit of normal.
Maintenance. The caps should be stored in the closed box.
Observers must not touch the pigments.
e
OCR for page 73
73
Calibration. The caps are taken from the Swedish Natural Color
System; their specification is given by Frisen and Kalm (1981~. No
calibration is required. Illuminant C must be used.
Reliability. No test-retest data are available.
Validity. This test is described by Frisen and Kalm (1981~. One of
the 20 normal control sub jects, who were aged 17 to 66 years, obtained
a score of 15. The upper normal limit was set at 10. Scores for
observers with congenital color defects ranged from 0 to greater than
50; 45 percent of the observers with congenital color defects had an
abnormal score. Scores for observers with acquired color defects
ranged from 0 to greater than 50; 90 percent of the observers with
acquired color vision defects had an abnormal score. A K comparing
pass-fail data for normal observers with acquired color vision defects
(either retinal disorders or optic neuropathies) gave a value of 0.85,
indicating good screening efficiency for acquired color vision defects.
Other Remarks. This is a new test that requires further validation
in the clinic. It offers a rapid and easy alternative to plate tests
in the assessment of acquired color vision defects.
Lantern Tests
British Board of Trade Lantern (1912)
12 filters of various reds, greens, and clears; Martin's Board of
Trade Modification (1938) (also known as Martin Colour Vision
Testing Lantern)--4 filters of green, clear, and 2 different reds;
and Martin's Board of Trade Modification Transport Type (1943~--5
filters of green, clear, yellow, and 2 different reds. Manufactured
by Kelvin, Bottomley, and Baird, Ltd., of Glasgow and London.
Not commercially available now.
General Description. In the 1912 model, the 12 lights (reds,
greens, and clear lights} varied within the limits approved for
navigation lights. The colors are shown singly or in horizontal
pairs. There are two aperture sizes (0.2 and 0.02 in.), which are
viewed at 20 feet to represent ships' lights at 200 and 2,000 yards.
In the 1938 model (redesigned for electric light) there were four
colors: one green, one clear, and two different reds. Again, these
are shown singly or in pairs, with the same two aperture sizes
available. The brightness of the lights is equated. A neutral filter
may be placed over the left light or over the right light to reduce its
luminance to one-third of its original value. In the 1943 model, a
yellow light was added to the lantern for use in testing transport
personnel.
e
OCR for page 74
74
Administration. The test is performed in a dark room at a distant e
of 20 feet. A voltage-controlled line is needed for the 1938 and 1943
models. The lights are presented in random order, and the observer
names their colors. Administration is complicated for the examiner
because of the many controls for selecting colored lights, aperture
size, single versus paired presentation, and, in the 1938 and 1943
models, the placement of a neutral filter.
Scoring. No standardized scoring method has ever been developed.
This is the primary disadvantage of this test for color vision.
Maintenance. No maintenance is required.
Calibration. No calibration is required. However, the replacement
bulb must be certified by the Physics Laboratory of London.
Reliability and Validity. No reliability or validity studies are
available.
Other Remarks. The lantern stimulates the navigation lights of a
ship and is used at a number of examination centers in the British
Commonwealth for the fishing fleet and merchant navy.
Color Threshold Tester
Color Threshold Tester, Stock No. 6515-388-3700, Macbeth
Corporation, P.O. Box 950, Newburgh, New York.
8 colored lights (2 reds, 2 greens, orange, yellow, blue, and
white) plus 8 neutral filters of various intensities.
Available from Macbeth Corp., P.O. Box 950, Newburgh, NY 12550
General Description. This lantern was developed for the U.S. Air
Force to determine quantitatively whether the color-defective applicant
was competent to make the color perception requirements of a particular
job. The colors of the lights were based on two considerations: (1)
some were colors close to the standards for aviation signal colors,
and (2) some were colors that would be difficult for the color-defective
person to identify. The lantern presents one light at a time, located
halfway between two blue guide lights. The eight colored lights are
presented at eight different luminances.
Administration. A demonstration of the eight colored lights is
-
given at the brightest of the eight luminances. The examiner then
turns the luminance knob to the dimmest of the eight luminances and
presents the eight colored lights consecutively, I1 to l8. The
luminance knob is then turned to increase the luminance to level 2, and
the colored lights are presented consecutively #8 to I1; the luminance
knob is turned to level 3 and the colored lights are presented
OCR for page 75
75
consecutively #1 to f8, and so on. The test is performed in a dark
room at a distance of 10 feet. It takes about five minutes to
administer the test. The observer names the colors presented.
Scoring. The exact color name is not always required for a correct
response: red must always be called red, but orange may be called
orange, yellow, or amber; green may be called green or blue; blue may
be called blue or green; yellow may be called yellow, white, amber, or
orange; and white may be called white or yellow. The part-score for
each of the eight colored lights is obtained by counting the correct
response, starting from luminance level 8 and continuing to lower
luminance levels until an error occurs. Correct responses at still
lower levels are not counted. The score for the entire test is the sum
of the eight part-scores. A perfect score, of course, is 64 and is
obtained by 95 percent of normal subjects. A score of 50 or better
(obtained by all normal subjects and 30 percent of defective observers)
is required for Class II or III medical certificates.* A score of 34
or better (obtained by 68% of defective observers) is required for
entrance to the Air Force Academy.
Maintenance. The cover in front of the stimuli should be closed
when the instrument is not in use, so that the filters will not become
dusty.
Calibration. No calibration is required.
Reliability. Sloan {1944) reports correlation coefficients for the
scores obtained by color-defective observers of 0.94 for same-day
sessions and 0.80 for different-day sessions.
Validity. The Color Threshold Test (CTT) was designed for
quantitative classification. Test scores of color-defective observers
show a broad distribution. Sloan (1944) has compared CTT scores of
defective observers with quantitative classifications obtained on other
tests. Paulson (1973) has compared CTT scores of 130 deutans and 94
protans with results on the Farnsworth Lantern and other tests.
Other Remarks. The method of administration (consecutive order f 1
to #8 at intensity level 1, and then consecutive order l8 to I1 at
intensity level 2, etc.) often results in two contaminants on the final
test score. First, the preceding colored light affects the observer's
response. For example, a particular colored light might be named
correctly for intensity levels 1, 3, 5, and 7 but incorrectly for
intensity levels 2, 4, 6, and 8 because it appears after different
*FAA requirements for medical certificates are described in Guide for
Aviation Medical Examiners,. Federal Aviation Administration (June,
1970).
1
OCR for page 76
76
colors in the two sequences. Second, the fixed pattern of administra-
tion (versus random administration) permits the observer to become
aware of the pattern after a few of the eight runs have been given and
also enables an observer to memorize the test.
Edridge-Green Lantern (1891)
4
7 colored glass filters and 7 modifying glass filters (ground
glass, ribbed glass, neutral glass, etc.)
Available from House of Vision, 137 N. Wabash Ave., Chicago, IL
60602. Replacement filters available from Clement Clark Ltd.,
London, England, and Hamilton Ltd., London, England.
General Description. The Edridge-Green Lantern is designed to
produce a range of colors and tints. In addition to the seven colored
and seven modifying glass filters, there are seven aperture sizes. The
colored filters represent signal colors; the modifying filters represent
smoke, fog, rain, and so forth; the various aperture sizes represent
color judgments made at different distances.
Administration. The test is performed in a dark room at a distance e
.
of 20 feet. The lights are presented in random order, and the observer
names the colors of the lights. Some of them are very difficult even
for those with normal color vision. Administration is complicated for
the examiner because the five rotating discs {containing the colored
filters, the modifying filters, and the apertures) can be rotated
singly or jointly, making hundreds of combinations possible.
Scoring. Although there are rules for the scoring, most often the
test resolves into a contest of color-naming wits between the examiner
and observer. ~
Maintenance. No maintenance is required.
Calibration. No calibration is required.
Reliabilitv and Validity. No reliability or validity studies are
available.
Other Remarks. This test is claimed to simulate railway signals
and is used in testing engine drivers in Great Br itian. It was used by
the U.S. Navy for qualification of midshipmen and line officers prior
to adoption of the Farnsworth Lantern Test in 1953.
Farnsworth Lantern (FaLant)
6 red, 6 green, and 6 white glass filters plus 9 dimming filters.
Available from Macbeth Corporation, P.O. Box 950, Newburgh, NY 12550
OCR for page 77
77
General Description. This lantern, developed for the U.S. Navy,
designed to pass normal trichromats and those persons whose color
vision defect is mild and to fail those with more severe defects. The
test is intended to select one-third of the color-defective population
for assignment to naval duties that involve color-judging tasks. Nine
combinations of red, green, and white lights are presented vertically
and in pairs. A dimming filter is combined with one of the lights in
each pair to reduce its luminance by up to 50 percent. Unlike other
lanterns that use lights that simulate navigational, aviation, or
railroad signal lights, the Farnsworth Lantern uses specific red,
green, and white lights that are confused by people with more severe
color vision defects. The reason for this choice was as follows. The
spectral characteristics of signal lights that are used for different
purposes {e.g., navigation or railroad signals) are different. Thus
"red" or "greens lights comprise a relatively wide variety of spectral
colors. Color-defective observers, however, confuse specific colors.
Therefore, they would find some red-green pairs easy to distinguish but
would be unable to distinguish other red-green pairs of lights. The
idea behind the Farnsworth Lantern, therefore, is that an individual
who can distinguish these pairs of lights which are known to be
confused by color-defective observers, will certainly be able to
distinguish all other pairs.
Administration. The test is simple to administer. All of the
instructions for administration, scoring, and operation of the lantern
test are printed as a metal plate affixed to the back of the instrument.
Examiners are cautioned that failure to follow all these rules will
result in invalid test results. The test is given in a normally lighted
room at a distance of 8 feet. The lights are presented randomly. The
observer reads a brief set of instructions and then names the colors
presented. The test requires less than one minute to administer.
_.
Scoring. If no errors are made on the first set of nine pairs of
lights, the observer is passed. If errors are made on the first run,
two more consecutive runs are presented, again in random order, without
a break or comments between runs. The errors on these last two runs
are averaged; an average error score of 1 or less is a pass score
whereas an average error score of 1.5 or more is a fail score.
Maintenance. No maintenance is required. The bulb does not burn
unless the examiner depresses the knob that rotates the lights. It is
a 1000-hour bulb with an automatic cutoff, and a replacement bulb is
located in the base of the instrument. The filters are very stable.
They have been found to have the same chromaticities for over 20 years.
Calibration. The chromaticity specif ications have been published
by Paulson (1973 ~ . No calibration is required.
Reliability. Test-retest data were presented by Paulson (1966)
The statistic of association, K, was 0.98.
1
e
.
OCR for page 78
78
Validity. The Farnsworth Lantern was designed to pass normal
trichromats and anomalous trichromats with good discrimination (i.e.,
mild discrimination losses). Some comparisons of Farnsworth Lantern
data with data from other tests in the NSMRL battery (pseudoisochromatic
plates, Farnsworth Panel D-15, and Farnsworth Panel H-16) are given by
Paulson (1966~.
Other Remarks. The Farnsworth Lantern Test is the final qualifying
test for the U.S. Navy, the U.S. Coast Guard Academy, and the U.S.
Merchant Marine Academy. It also may be used by the U.S. Army for
qualification of pilots and by the U.S. FAA Aviation Medical Examiners .
In addition, it is used by some U.S. railroad systems and other
organizations.
Other Tes ts
Holmgren Wool Test
Wool skeins
Available from:
1. Bernell Corp., South Bend, IN 46601 -
2. House of Vision, 137 N. Wabash, Chicago, IL 60602
General Description. The Holmgren Wool Test was one of the
original tests designed to screen red-green color defects. The test
consists of 75 small strands and three large strands of colored wools.
The large strands serve as test colors, the small strands as comparison
or matching colors. There is no identification of the skeins. An
instruction sheet accompanies the test, but there is no scoring sheet
or scoring instructions.
Administration. The skeins are placed in a heap. One test skein
is selected. The subject is asked to select skeins from the heap that
most nearly match the test skein in color. There is no exact match;
similarly colored skeins, or skeins of lighter or darker shades of the
same color, may be selected. The procedure is repeated for each test
skein.
Scoring. There are no scoring instructions. The examiner looks
for hesitation and for the selection of dissimilarly colored skeins
~ e . g ., for the red test skein , the selection of other colors , such as
green, blue, brown, or yellow skeins ~ .
Maintenanc_. The yarns are subject to fading when exposed to light
or dust. Handling should be avoided. The set should be kept in the
cardboard container when not in use.
Cal iteration . Sample spectrophotometric data have been reported by
Rasmussen and Lakowski (1978 ~ . The skeins vary considerably from set
e
OCR for page 79
79
to set . No calibration is required by the user . The illuminant is no t
specif led.
Reliability. No data are available .
Validity. No data are available.
Other Remarks. This test is primarily of historical interest. It
is not recommended as a suitable screening test.
Lovibond Color Vision Analyzer
27 glass filters
Available from Tintometer Ltd., Salisbury, England
General Description. The Lovibond Color Vision Analyzer presents
2 7 colors in a circular display with a central neutral gray. The
colors subtend 1°, complete the full color circle, and are arranged
in random order in the display. The luminance of the central gray
slide is variable. The colored lights may be desaturated by the use of
superimposed white light. Instructions are included.
Administration. For a given luminance and saturation level, the
l
observer indicates which colors on the circle match the central neutral
slide.
Scoring. The examiner notes which colors are chosen as a match to
the neutral slide at each saturation level. Normal observers select
colors in the yellow-green and blue-purple regions at low saturations.
The saturation level for which colors are accepted as neutral increases
with age (Ohta, Kogure, and Yamaguchi, 19781. Congenital red-green
color-defective observers select colors in the blue-green and red
regions: dichromats select two or more colors at all saturation
levels; anomalous trichromats select two or more colors at medium
saturation levels. The actual colors chosen are diagnostic of the
color defect: nos. 1 and 14 are protan confusion colors; nos. 2 and IS
are deutan confusion colors.
Maintenance. The tintometer glass is very durable and lasts for an
extended period of time. The lamp itself, however, has a limited life
usually only 30 hours).
Calibration. The chromaticities of the filters are given in the
instructions. No calibration is required of the user.
Reliability. Reliability is good for normal and dichromatic
observers but poor for anomalous trichromats due to poor control of the
desaturation device (Pokorny et al., 1979~. Data for calculation of
are not available.
1
e
OCR for page 80
80
Validity. The test distinguished normal from red-green
color-defective observers (rain, 1974; Ohta, Kogure, and Yamagochi,
1978~. The following classification data were given by Ohta, Kogure,
and Yamagochi (1978~.
Test of
Qualitative classification
.65
Quantitative classification .88
The K for qualitative classification is not good, the major problem
being misclassification of protan observers. All deuteranopes were
correctly classified. Deuteranomalous trichromats were classified
correctly as such in 90 percent of cases and were incorrectly classified
as deuteranopes in 10 percent of the cases. Protans were as likely to
be classified deutan as proton. Therefore the test cannot be used for
qualitative classification. Dain (1974) previously reported excellent
qualitative classif ication but gave no statistics. Quantitative
classifiction by Ohta, Kogure, and Yamaguchi (1978) are consistent with
Dain's results. e
Representative terms from entire chapter:
anomalous trichromats
