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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

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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.

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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.

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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

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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

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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

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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

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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.

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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

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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).

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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.

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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.

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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

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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

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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

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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

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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

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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

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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 .

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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

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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

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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