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CHAPTER 4 USING COLOR VISION TESTS EVALUATION OF CONGENITAL AND ACQUIRED COLOR VISION DEFECTS The hereditary nature of color vision disorders was recognized at the end of the eighteenth century. In the nineteenth century there were major disasters with loss of life in the shipping and railroad industries. These tragedies were attributed to the failure of engineers to recognize a colored signal. As a result, people with congenital red-green defects were and still are excluded from positions as pilots or engineers in commercial air, sea, and rail transport and similar duties in the armed forces. Tests that were developed to evaluate color vision were both practical and empirical. While the anomaloscope remains the only clinical method for precise diagnosis of the presumed genetic entities, many tests have been devised for quick, inexpensive, and efficient screening of the color-defective population Screening tests are used to identify individuals who may eventually require more extensive color testing. Their usef ulness is in the identif ication of such individuals rather than the diagnosis of the color def eat. ~ ~ of modes t cost . . Screening tests are easy to administer and score and are Rapid Screening of Congenital Red-Green Color Defects Rapid screening of red-green color defects may be necessary in the military, schools, or transportation and other industries. The most effective test for rapid screening is one of the validated plate tests designed for this purpose including the Tshihara, Dvorine, AO H-R-R, and other series of pseudoisochromatic plates that detect about 96 percent of the cases confirmed by anomaloscoPe (Table 4-l). It is common to rely on a single test or even on a few selected plates. It should be noted that some normal subjects read the hidden digits of the Ishihara test; and, of course, some normal subjects will misread occasional plates. The deuteranomalous trichromat with good discrimination may pass the majority of a set of plates. We are not aware of any screening test employing colored slides of transparencies that has been adequately validated. It is inappropriate to attempt to make a ~home. screening test by color photography of an 81

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82 TABLE 4-1 Screening for Congenital Red-Green Defects Using Plate Tests Status Test Validated Not intended for screening Unsuitable due to poor validation AO Plates AD H-R-R Plates Dvorine Tshihara Tokyo Medical College City University Titmus Color Perception Test Bausch and Lomb Ortho-Rater Keystone Telebinocular existing plate test. Color reproduction is affected by the type of film, the illuminant used for photography, the color processing, and the illuminant used to project the transparency. Color processing to precise standards is very difficult. Although in the future color screening tests may be produced using colored transparencies, any such test will require adequate spectrophotometric control as well as validation in the population. Diagnosis of Red-Green Defects Anomaloscopes may be used for diagnosis of red-green color vision defects. The anomaloscope is the only clinical instrument for diagnosis and classification of the presumed Genetic entities of dichromacy and to both simple and extreme anomalous trichromacy as defined by Franceschetti (1928). Anomaloscope examination is t~me- consuming, and only a trained person can use the anomaloscope. The test must include a full examination of the matching range, it is inappropriate to allow one or two matches. an aaa~tlona1 problem Is that commercially available anomaloscopes are very expensive. Plate and arrangement tests are not entirely successful at diagnosis of congenital red-green defects. The failure of plate tests results from the fixed color relations of figure and background. There is sufficient variation in the color vision of defective observers that a proton observer may fail a deutan diagnostic plate or vice versa. Confusion axes on arrangement tests similarly may show ambiguity. The characteristic error axis on the FM 100-hue test may not occur if the color-defective observer makes relatively few errors.

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83 Recognition of Congenital Blue-Yellow Defects and Achromatopsia Recognition of congenital blue-yellow defects requires the use of one or more of the tests designed for this purpose. Plates for blue-yellow defects include the AO H-R-R, the Tokyo Medical College plates, and the Farnsworth F: plate. Normal observers with heavy ocular pigmentation may miss the green symbol on the F2 plate and appear to show a tritan defect. Failure to perceive the blue symbol usually seen by normal observers and tritans is indicative of congenital red-green defect. The F2 plate should be used in conjunction with another test. Recently, van Norren and Went (1981) suggested that detection of a blue increment pulse on a yellow background provides a sensitive and efficient test. The Farnsworth Panel D-15 and the FM-100 hue test are important in recognition of blue-yellow defects. Evaluation of Acquired Color Vision Defects The detection and classification of acquired color vision defects may be accomplished by use of an anomaloscope combined with a test that measures chromatic discr imination. In addition, 8 to 10 percent of males with acquired color defects have a concomitant congenital color defect; the examiner should be alert to this possibility. Plate tests are of variable usefulness in testing acquired color defects. An observer with an acquired color-defect may not give the expected reading; that is, read the numbers designed for normal or congenitally defective observers; misreadings may occur. If an observer with reduced visual acuity fails a plate test, the examiner cannot conclude that there is a specific kind of color defect. Further analysis is necessary. Arrangement tests are of particular importance in acquired color vision defects. The Lanthony Panel D-15 and Lanthony New Color Test were designed specif ically for evaluation of acquired color vision defects . CLASSIFICATION AND QUANTIFICATION OF CHROMATIC DTSCRIMINATrVE ABILITY In some applications it is important not only to screen for color defects but also to classify the defect according to chromatic discriminative ability. Test Batteries Many examiners decide on a test battery to fulfill their specific requirements. Choice of a test battery reflects the testing require- ments, the availability of tests, the personal experience of the examiners, and the time available for testing. e

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84 An example of a test battery for congenital red-green defects is that designed at the U.S. Naval Submarine Medical Research Laboratory (Paulson, 1973) (Table 4-21. The battery includes the use of a set of plates, lantern, arrangement tests, and an anomaloscope. The battery allows recognition of congenital red-green color-defective observers and separation of color-defective observers into four categories: individuals showing (1) mild, (2) moderate, and (3) severe loss of chromatic discrimination, and those showing (4) dichromatic color vision. The mild and moderate categories tend to be predominantly simple and extreme anomalous trichromats; the severe and dichromat categories include individuals who are extreme anomalous trichromats and dichromats. The correlation is not perfect since chromatic discriminative ability varies widely among anomalous trichromats. The NSMRL test battery will not necessarily predict the performance of the defective observer on other color tasks (Kinney et al., 19791. Verriest (1968b) proposed a test battery (Figure 4-1) for evaluation of congenital defects that includes the Ishihara, F2 plate, AD H-R-R, Farnsworth Panel D-15, Lanthony Desaturated Panel TABLE 4-2 NSMRL Test Battery for Determining Degree of Color Vision Defect . . . - Class Pseudo- D-15 H-16 isochromatic FaLant Test Test I. Normal trichromatic Pans Anomalous trichromat (mild defect) Fail Pass Pass Pass Pass Pass Pass III. Anomalous trichromat {moderate defect) Fail Fail Pass Pass IV. Anomalous trichromat (severe defect) Fail Fail Fail Pass V. Dichromat Fail Fail Fail Fail Source: Paulson (19731.

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85 I. Test battery for congenital color vision defect (Verriest, 1968b) A. Ishihara (16- or 24-plate editions) B. F2 C. AO H-R-R D. Farnsworth Panel D-15 E. Lanthony Desaturated Panel D-15 (if Farnsworth Panel D-15 is normal) F. Nagel Model I anomaloscope II. Test battery for acquired color vision defects (Pinckers, 1978a) A. Initial screening 1. AO H-R-R 2. Lanthony New Color Test - Box 6/4. a. If Box 6/4 failed, do Box 6/8. b. If Box 6/4 passed, do the Desaturated Panel. B. Red-green defects revealed by initial screening 1. Ishihara 2. FM 100-hue 3. Nagel Model T anomaloscope C. Blue-yellow defects revealed by initial screening 1. F2 2. FM 100-hue 3. Pickford-Nicolson FIGURE 4-1 Test Batteries for Congenital and Acquired Color Defects D-15, and Nagel Model 1 anomaloscope. It was suggested that the Lanthony Desaturated Panel be used when the Farnsworth Panel D-15 gives normal results or shows only minor errors. This battery allows good differentiation of protanomaly, protanopia, deuteranomaly, deuteranopia, tritan defect, and achromatopsia. Pinckers (1978a) proposed a battery for diagnosing acquired color vision defects in the ophthalmology clinic. This battery, also shown in Figure 4-1, includes the AO H-R-R, Lanthony New Color test, F2 plate, Ishihara, FM 100-hue test, and both the Nagel Model I and Pickford-Nicolson anomaloscopes. The minimal requirement for an eye clinic should include a screening test, the Panel D-15 or Lanthony New Color test, the FM 100-hue test, and an anomaloscope. If the screening test does not include blue-yellow Plates, the F: plate may be added. - Quantification of Chromatic Discriminative Ability Typically it is not appropriate to use the number of errors on a screening plate test as a numerical indication of chromatic discrimina- tive ability. Color-defective observers fail a screening plate because -

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86 to them the colors in the f igure match those of the background . Fo r most tests, the colors in the figure and background were chosen empiri- cally on a few "test" observers. There is considerable variation among color-defective observers, and the optimal colors for figure and back- ground will vary among these observers. A color-defective observer with poor chromatic discrimination may make few errors on a screening plate test because the color vision of his eye differs from that of the observers on whom the test was optimized. Conversely a color-defective observer with good chromatic discriminative ability still may fail many of the plates if the colors happen to be optimized for his eye. The Dvorine is one plate test for which it is specifically recommended that the number of errors in reading the plates gives an estimate of severity. However, we were not able to find data evaluating the class) fication of severity on the Dvorine plates from which the statistic of association, K, might be calculated. The Farnsworth-Munsell 100-hue test has been used as a quantitative test of chromatic discrimination even though its designer, Dean Farnsworth, originally suggested only that observers could be specified as showing superior, average, or inferior chromatic discriminative ability. It is generally accepted that the test involves not only chromatic discriminative ability but also cognitive parameters, such as concentration, patience, and cooperation. It is appropriate, however, to compare an observer's error score with a set of population norms, and there are some cases in which it is appropriate to use the number of errors on the FM 100-hue test in a quantitative way (see Arrangement Tests,. in Chapter 3~. - SCREENTI* FOR PROFESSIONAL PURPOSES The choice of a test is dependent on both color vision requirements and t _ availability. It must be decided whether to choose only those observers with good discrimination. Such decisions are important because the exclusion of dichromats, for example, does not ensure that all selected observers will have good color discrimination. After careful consideration, it may become obvious that not all defective observers need to be excluded or, alternatively, that it is unnecessary to select only the best for the task. There are professions and skills in which good discrimination is advantageous but in which a defect is not an insurmountable handicap. Of course there are situations that require good discrimination, and in these occupations it is absolutely necessary that only those with good ability be selected. Even when color vision requirements are known, one must consider the availability of tests, money, and time, and whether the examiner possesses or is willing to acquire the skills that would enable him or her to administer validly the more complicated tests. Finally, it may be necessary to design a field test rather than use a clinical color vision test; for example, when an employee is required to reject a production line item whose color differs from a standard given tolerance step. Preliminary screening may be used to eliminate observers with congenital defects. Because each clinical test measures a specific

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87 ability, the task required of the color worker must be considered. if the task involves the perception of small saturation differences, an appropriate test is the Color Aptitude test. If small color differences must be distinguished, the FM 100-hue test may be used. If the task involves metameric matching, such as in color mixing in the textile and or inning industries, the anomaloscope should be used. The screening of candidates for some occupations is performed best by means of specialized field testy that reproduce the actual Eli hiring "n - Anti - r - ~ an the Ah am _~ _ea __ ~_~ ~ For example, the ability to recognize colored signals is evaluated best by a field test using signal equipment. It is extremely important, however, that any such field test be standardized. The same distance, illumination levels, number of stimuli, and so on, should be used for all candidates. The ability to sort materials by color (e.g., cotton, diamonds, pearls, and gasolines) is evaluated best by a field trial using real materials; the materials should be identical to those encountered in the job situation, and the type and level of illumination must be exactly replicated. TEST ADMINISTRATION: TRAINING PERSONNEL TO ADMINISTER TESTS The majority of clinical color vision tests are designed for use by personnel with minimal training in color vision testing. Instructions are provided with many plate and arrangement tests; in most cases, careful reading of these instructions will provide sufficient informa- tion for correct test administration. Scoring of the FM 100-hue test is somewhat complicated, especially when error scores are high. The manual accompanying the test, however, provides ample instruction. Plotting the errors is somewhat easier using the technique described by Kinnear (1970~. Lantern tests are designed for easy administration. The major exception among clinical tests is the anomaloscope: adminis- tration of an anomaloscope examination requires knowledge of calorimetry and/or extensive training in use of the instrument. Anomaloscooe exami- nation should not be attempted by unskilled personnel. The procedures detailed in the section on anomaloscopes in Chapter 3 must be followed. Even when the instruction manual for a given test is understood, there are a number of precautions that personnel must follow: Use a standard procedure. Standardized procedures and conditions must always be used during administration of clinical tests, such as the FM 100-hue test, pseudoisochroma~ic plates, or the anomaloscope. The level and type of illumination must be constant. A fixed set of verbal instructions must be read to the observer, since variation in instruction might bias responses._ The use of color names should be avoided e Use of a standard procedure allows comparisons to be made between data collected by examiners in other clinics or even by the same examiner on different occasions. Recommended procedures for each test are detailed in Chapter 3. Follow scoring instructions carefully. The test must be scored according to the instructions that accompany the test. The score sheet should contain the following type of information: r

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88 Personal data: e.g., name, address, telephone Birth date, sex Testing information: date of test, illuminant (for plate and arrangement tests), monocular (which eye) or binocular Data relevant to testing situations: occupation, visual acuity, etc. For plate tests, a sample scoring sheet may be provided; if not, one must be designed. In addition to the information above, a scoring sheet should include a place to record the response to each plate. It is helpful if the sheet indicates the expected responses of normal and color-defective observers. A good score sheet indicates to the examiner how to interpret the result. For the anomaloscope, the examiner should note the test brightness setting made for each mixture ratio. The examiner should also note whether the setting was accepted as a color match and if not, why not (for example, too much red or too much green in the mixture field). Match the test to the ability of the observer. m e majority of color vision tests are designed for use with observers who are not familiar with the specific test or testing procedure. Patients or prospective employees may be nervous about the testing situation. Thus test results may be biased by cognitive or emotional factors. Cognitive_ factors of some tests may be beyond the capabilities of some patients, e notably individuals with other visual, motor, or intellectual handicaps, the elderly, and the very young. Furthermore, the majority of color vision tests were designed for use with young adults with normal visual acuity. Personnel administering clinical tests should be made aware of these factors and be prepared to deal with the occasional ~difficult" observer. Do not allow observers to wear tinted classes or tinted contact lenses. Color testing should not be performed on observers wearing tinted glasses or tinted contact lenses. Tinted glasses are easily identified. The examiner should ensure that tinted lenses are not being worn. Tinted contact lenses may not be noticed; all observers should be asked if they wear such correction. Some contact lens wearers also have regular clear glasses. In this case, an appointment should be made for a future date, and the observer should be told to wear the glasses rather than the contact lenses. The majority of screening tests can in fact be performed with glasses or contact lenses removed. Spherical refractive errors of two or three diopters should not cause difficulties for screening plates if the patient is myopic or is hyperopic with adequate accommodative ability. Refractive error of myopes is often reduced on first removing the hard contact lens. If necessary, an observer may use a hand-held ophthalmic lens for screening plates or ophthalmic trial frames for arrangement tests. The Nagel Model I and Neitz anomaloscopes have adjustments for focus.

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89 Decide whether to use monocular or binocular testing. Few manuals specify whether testing should be monocular or binocular. In research it is customary to test one eye at a time. In the eye clinic, it is especially important to check each eve separately, since eye diseases mat affect the eyes to a different degree. On the other hand, routine screening as performed in schools or in the military is usually performed binocularly. What to do when tests given different results: Occasionally an observer will fail one set of screening plates and pass another set. Alternatively, an observer may show a defect on screening plates but not on the anomaloscope or vice versa. If any set of screening plates is failed the observer is considered to have a color defect. An anomaloscope examination is required to provide further classification of the defect. Observers who show this behavior include anomalous trichromats with good chromatic discrimination. These individuals are called minimale anomalen (Pokorny et al., 1979~. Additionally some normal trichromats may show minor color abnormalities (Pokorny et al., 19797. The majority of normal trichromats with minor color defect show generally poor color discrimination and will not only fail color screening tests but show abnormal error accumulations on discrimination tests. Rarely, normal trichromats will fail a screening test but show no other sign of color defect. SOME SPECIAL PROBLEMS OF TESTING Color vision tests were designed by adults for use with adults with normal visual acuity. Some adults (e.g., illiterates, observers not fluent in the examiner's language, or the elderly J may present the examiner with special problems. Testing of children also requires special attention. The testing of a suspected malingerer or concealer also may present problems. The general rule is to use common sense and to perform a test only if it is clear (1) that the observer understands the procedure, and (2) that the test can be performed using appropriate techniques. Testing Illiterates Illiteracy is relatively rare in countries with compulsory grade-level education. Illiteracy, however, may be encountered in less-developed countries, especially by researchers interested in genetic studies. The problem of illiteracy may then be compounded by language difficulties. If some mutual understanding is reached, tracing of screening plates is still appropriate. The Ishihara test includes tracing patterns for illiterates; the symbols on the AO H-R-R may be traced with a brush, as may the numerals on the other plate tents. Anomaloscope examination may prove difficult unless the observer understands the task.

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so Language Problems Examination of adults not fluent in the examiner's language may be difficult if no translator is available . With good will and by mimicry and sign language, a foreign-speaking individual may be tested on screening plates. The observer should either trace the symbols with a brush or write down the symbol or numeral on an adjacent piece of blank paper (not the score sheet). Alternatively a matching technique may be used in which drawn or cutout outlines of the figures are prepared for the observer to point at or superimpose on the plate. Arrangement tests and anomaloscope examination require a better level of communication. Testing the Elderly With respect and consideration, the elderly individual should offer no problems in testing. The arrangement tests may be difficult for individuals with poor manual dexterity, such as those with arthritis. Such individuals may drop the chips and become embarrassed or impatient with the task. Again the solution is common sense. Perform only those tests that are necessary for diagnosis and that are within the patient's abil ity . Bifocal prescriptions may offer a problem in anomaloscope testing. The observer may have trouble finding the field in the telescope view of the Nagel anomaloscope or may wonder which part of the bifocal to use. The observer should always look through the part of the bifocal lens that is intended for distance use, usually the upper half of the lens. In some cases, removing the glasses and using the telescope adjustment may be all that is needed. In ether cases, the observer may prefer a hand-held ophthalmic trial lens of the appropriate power for distance vision rather than the regular glasses. It is important to ensure that the dividing line of the split field appears clear. The Pickford-Nicolson anomaloscope should offer fewer difficulties to bifocal wearers. Testing Children Children under 12 years of age offer special problems in color testing, since many of the tests require intellectual abilities that develop at different ages: screening tests require knowledge of the alphabet or numerals; arrangement tests require the concept of serial ordering. The situation is even more difficult in the case of retarded children. With increased use of color coding in school materials, it is of growing importance to identify congenital color defects in young children. Many observers with a congenital color defect retain memories of being treated as ~stupid. or ~troublemakers. because they had difficulties making color discriminations that were immediately evident to color-normal observers (Sloan, 1963~. Color tests may also be.helpful in identifying hereditary retinal disease in children.

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91 There are three tests designed especially for children: the Guy's Hospital color vision test,* the Matsubara test,** and the Titmus pediatric color perception test. The Guy's Hospital color vision test contains design flaws that make it ambiguous and confusing to adults, and thus presumably equally confusing to children (Alexander, 1975~. The Matsubara test contains symbols of items that are familiar and important in Japanese culture (e.g., cherry blossoms) but that are not necessarily familiar to American children. To date, none of these tests has received full validation in an American population. Although a review of the literature revealed rather variable results in testing young children (Alexander, 1975; Verriest, 1981), it is possible to test children successfully with the adult tests, such as the AO H-R-R and the Ishihara screening tests. Care is needed to match the task to the age, attention span, and intellectual development of the child. It is important to give careful instruction to ensure that the child understands what he or she is asked to do. Such instruction should not contain reference to color names or color differences that the color-defective child may not understand. By their very nature, color tests are frustrating and difficult for color-defective observers, and this point must be remembered when dealing with color-defective children. Pre-school and Kindergarten Children (3 to 5 Years old). Today with increased use of pre-schools and educational television, many children of 3 to 5 years know alphabet letters, the numerals from 1 to 10, and simple geometric shapes, as well as the concept of "same" and "different. " Young children may be tested with the AO H-~-R test (Alexander, 1975~. If necessary, the examiner may draw the three symbols--triangle, circle, and cross--on a sheet of paper and ask the child "Do you see any of these shapes on the color plate?. If the child says eyes n he or she is asked to point first to the quadrant of the plate in which the child sees the symbol and then to the symbol on the sheet of paper that matches the symol seen on the plate. It is important to practice the procedure with the demonstration plates and to muke certain that the child distinguishes the three geometric shapes. The AO H-~-R is preferable to the Ishihara or Dvorine with young children even if they know some numerals, since many children of this age will confuse certain numerals and will not be sure how to identify a double-digit numeral. For example, when shown a plate containing the numeral .26,. the child may say .6. or .2. or even .9~ not knowing that the numeral is called Twenty-six. The alternative of using the tracing patterns designed for illiterates is not optimal, since few *The Guy's Colour Vision Test for Young Children by Peter A. Gardiner, M.D. **Colour Vision Test Plates for the Infants, originated by Hiro Matsubara and revised by Koku Kojima. Tokyo, Handaya Co., Ltd.

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92 young children have the necessary manual dexterity to perform an accurate tracing. . First- and Second-Grade Children (6 to 8 Years old). Many children of 6 to 8 years can perform the screening tests. However, few children in this age range understand the concept of serial ordering or have the attention span necessary to complete a serial ordering test such as the Panel D-15 (Adams et al., 1975; Cohen, 1976~. A 6-year-old may start the Farnsworth Panel D-15 correctly and make minor errors after a few caps, or may put two favorite colors together. In addition to the plate tests, a limited amount of information may be obtained from 6- to 8-year-olds on an anomaloscope. The Pickford- Nicolson anomaloscope has the advantage that both child and examiner can point to one or the other side of the vertically split field, thereby eliminating the need to describe what is seen. The Nagel anomaloscope has a disadvantage in that some children have difficulty aligning themselves to see the field in the telescope view. The examiner should set both the color mixture and brightness and ask the child, Ado you see a circle of color, or can you tell that there are two colors in the circle?. The examiner must present matches that have an obvious brightness difference (green primary and yellow turned dim), matches that are representative of a normal trichromat, and matches of the common red-green defects. ~ . Children of 8 to 11 years can usually perform the screening tests and the Farnsworth Panel D-15. They will perform on the anomaloscope If the examiner sets the color mixture and watches carefully how the child sets the yellow brightness; the examiner should set it also, if necessary. Children of 8 to 11 years can perform the FM 100-hue test; however, many become bored after one or two boxes, with a consequent performance decrement. Mentally Retarded. Plate tests are not suitable for screening in the mentally retarded population. Color screening of mentally retarded boys (with plate tests) revealed a high failure rate (20 to 30%} with poor inter-test correlations (Salvia 1969; Salvia and Ysseldyke, 1971a, 1971b; 19721. The high rates represent failure of screening plates by mentally retarded boys with normal color vision defined by anomaloscope. The problems are evident in AD H-R-R, Dvorine, and Ishihara. Arrangement tests, such as the FM 100-hue test and Farnsworth Panel D-15 (Salvia, 1969), also offer difficulties and may reveal high incidences of apparent color defect. Salvia and Ysseldyke (1971a,b) report an incidence of 8.7 percent for congenital red-green color defects when the Pickford-Nicolson anomaloscope was used. If the examiner is confident that the mentally retarded individual understands the anomaloscope test, this test may be used for evaluation of color vision in the mentally retarded population. e

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93 Malingering and Concealing Two contingencies that arise occasionally include the person with normal color vision who claims to have a color vision defect (either by malingering or-due to hysteria) and the person with a congenital vision defect who wants to pass a color vision test (concealment). The malingerer is the more difficult to detect. Malingering and Hysteria. Malingering can occur in connection with the assessment of workmen's compensation after an industrial accident. Hysteria reflects a psychosomatic basis. It can be difficult to detect malingering and hysteria. One way of revealing malingering or hysteria is by use of tests such as visual fields and electroretinography. Generally a battery of tests is used, in which case the observer tends to produce atypical or contradictory results. The malingerer may claim that he is unable to read any of the pseudoisochromatic plates, including the demonstration plates. If visual acuity is good, failure of the demonstration plates is indicative of malingering or hysteria. On tests such as the Panel D-15 or the FM 100-hue test, the malingerer will arrange the samples haphazardly. High error scores of 400 or more without predominant axis in an adult with normal visual acuity are indicative of malingering. The malingerer gives inconsistent answers on anomaloscope examination. Acceptance of H impossible matches by an adult is indicative of . malingering. The most difficult cases occur when malingering or hysteria is superimposed on a preexisting congenital or acquired color vision defect (Kalberer, 1971; Pickford, 19721. A comparison of the color vision test results with other visual functions such as visual acuity, dark adaptation, and visual field, may be necessary. Concealing. A person who deliberately tries to conceal a congenital color vision defect usually wants to be accepted for a job in which normal color vision is a prerequisite, such as in shipping or air transport. That person may have a good chance if the correct answers to a set of screening plates are provided and learned in advance (Perdriel et al., 1975; Verriest and Hermans, 1975~. Some defective observers may use tinted glasses or tinted contact lens (e.g., the X-chrom lens) to read pseudoisochromatic plates. It is difficult or impossible to conceal successfully on a properly administered anomaloscope test. COLOR VISION ~CURES. AND ~REMEDTES. Many cures and remedies for red-green color vision defects have been reported in the newspapers, in lay magazines, and even in professional journals. Attempts to cure color vision defects reached a peak during World War II because of the number of young men with red-green color defects who were eager to be accepted into the Navy, Air Force, and office training programs. Some of the alleged cures and remedies, none

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94 of which proved to be successful under control investigation, included warming one eye; staring at flashing red and green lights; wearing colored goggles; being coached in color naming and color matching; and taking injections of iodine, staggering doses of various vitamins , and injections-of extracts from cobra venom, marigolds and lobsters. A two-volume book for testing and training color-defective observers, which was published in 1944, claimed that people with color vision defects were merely visually confused and needed to identify their confusion and then correct it by training. Other reports described color-defective observers who were able to pass the color vision test for the military after extensive training on the test. In 1946 the Army-Navy National Research Council Vis ion Committee r equested from the American Committee on optics and Visual Physiology (ACOVP) a statement of the efficacy of corrective training . The statement was adopted by the American Academy of Ophthalmology and Otolaryogology, the American Ophthalmological Association, the Section on Ophthalmology of the American Medical Association, and the Association of Schools and Colleges of Optometry. Its conclusions are still valid: No method had been found for the correction of color blindness, whether called 'color weakness,' 'color confusion,' or 'color defectiveness.' Men can be coached to pass tests, but their physiologic deficiency cannot be repaired. Any claims to the contrary, any treatment which convinces operators that they can see colors they ~ could not see before will decrease safety in transportation, decrease security in national defense, and decrease efficiency in industry. (quoted in Farnsworth and Berens, 1948~. Since that time, several other techniques for improving color vision have been proposed. One of them involves wearing a color filter, in the form of a contact lens, over one eye. With the use of this lens, which is called the X-chrom lens, the two eyes receive different spectral distributions of light. Because of the relative changes in lightness that the filter produces, the lens may help the color-defective observer to make chromatic discriminations and to pass some color vision tents. However, neither the X-chrom lens nor any of the other color vision cures and remedies that have been proposed can restore normal color vision function. The working group is aware of no scientific study demonstrating that performance of complex real work tasks by people with defective color vision would be enhanced by use of the X-chrom lens. Siegel (1981) has discussed hazards potentially associated with use of the X-chrom lens for tasks such an automobile driving. ACOVP has recommended that examiners be extremely cautious in deciding whether to allow persons to use such devices when being tested for color vision required for occupations (quoted in Siegel, 1981~. e