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CHAPTER 1 - INTRODUCTION Color vision tests are used for a wide variety of purposes. Some of these include the rapid screening of congenital red-green defects in industry, transportation, and the military. The classification of discrimination ability within the population of congenital red-green defects is used for job assignment purposes. Another use for screening involves the recognition and diagnosis of congenital disorders for psychophysical or genetic study. In the the clinic, screening is used for the recognition and differentiation of congenital and acquired disorders, for the classification of acquired disorders in patients with eye disease, and, in some cases, for the assessment of treatment or for tracking recovery from disease or trauma. Finally, in education and industry, screening for both color vision defects and color apti- tudes is used for vocational guidance in occupations or professions that require color judgments. The two major problems faced by those who use color vision tests are (1) to know the color vision requirements of a given task and (2) to select appropriate color vision tests. COLOR VISION REQUIREMENTS IN DIFFERENT OCCUPATIONS it is essential for the benefit of both employer and employee that the color vision requirements of a job be adequately described. On the basis of these professional requirements and observer capabilities a decision can be made about whether an individual's color vision is suitable for performing the particular duties encountered in daily work situations. Such practical assessment of the relevant color qualifications helps to prevent the inappropriate allotment of manpower. A major difficulty in this regard is the lack of precise checklists of color vision requirements for different jobs; there are no guidelines to help employers establish color requirements for a given job. Broadly speaking, however, many occupations can be divided into three categories (e.g., Lakowski, 1968) depending on the quality of color vision required: 1. Those excluding major color defective observers; 2. Those requiring representative color vision ; 3. Those requiring good color discrimination. 1
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i 2 Occupations Excluding Major Color Vision Defects There are many activities and occupations in which defective color vision is either undesirable or unacceptable. Generally observers with severe color defects should not be expected to work in any industrial situation in which a premium is placed on the recognition and/or classification of color surfaces, lights, or objects. Abnormal color vision is therefore a serious handicap in all those areas of electronics and telecommunications that involve the identification, coding, and wiring of electrical equipment. The exclusion of major color-defective observers is also essential in transportation industries (railway, marine, or aviation) in which confusion of signal lights can endanger public safety. On the other hand, not all professions that validly exclude major color defective observers require normal color vision. Individuals with mild impairments can perform many operations involving color discrimination without any special risk to their own or to public safety. Occupations Requiring Representative Color Vision There are a vast number of occupations in which the mere exclusion of color-defective observers is an inappropriate policy for selecting personnel. In industry, especially, it seems more important to discover whether a person is fit for a particular job than to classify him or her as either normal or color defective. What is required in most situations is to establish whether the employee has the necessary skill to deal with a particular color task or to satisfy some criteria acceptable to the employer. In such areas as color research, commercial painting, color photography, chemistry, papermaking, paint mixing, the graphic arts, lithography, cartography, and textile dyeing, it is especially important that those who must make color matches have color vision that is representative of the majority of consumers. It is well known that color-matching ability may vary considerably from one observer to another; those observers who fall at the extremes of the distribution of normals may be considered to have an atypical form of normal color vision. Usually such deviations from the mean are not diagnosed by routine testing, yet they may constitute serious practical color vision problems by reducing the individual's effective job performance. Occupations Requiring Good Color Discrimination In many professions, individuals are chosen for their ability to make fine or difficult decisions in color discrimination. Here the exclusion of color-defective observers is not the prime consideration. Rather, people are selectively chosen for their precision in matching sample colors to standards or in classifying colors that differ only very subtly. In addition, in some occupations the recognition of color at twilight levels of illumination is required. Only individuals with e
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3 good color discrimination or specific aptitudes can perform these types of jobs with facility and accuracy. SELECTING COLOR VISION TESTS It is possible to design appropriate task-specific field tests in order to establish the color vision requirements of different jobs, but such a job-by-job analysis would be inefficient and expensive. On the other hand, selecting an available clinical color vision test for a particular application is not simple. First, information concerning the merits of these tests relative to each other and to various job requirements has not been readily available. Second, clinical color vision tests are not designed for the scaling of performance or for multiple cutoff criteria; the scoring standard for most clinical tests is stated in terms of a single pass/fail score. Third, the classification of color discrimination ability by clinical tests might not predict performance in a real-life situation (Kinney et al., 1979~. Many experts feel that to generalize from a clinical test to a job requirement is inappropriate at best and meaningless at worst. Fourth, the determinants of perform- ance on each test are sufficiently complex, ranging from calorimetric design to motivational factors, that no test can be considered to provide a single metric of color vision. In the absence of good population studies that relate job perform- ance measures to test scores in batteries of color vision tests, these problems might be essentially insolvable. However, an understanding of the existing color vision tests may help an employer who is familiar with the job requirements to decide whether to use a clinical test or to have field tests designed to his specifications. This report surveys the existing clinical tests of color vision and gives some general indications as to their design and use. 1