3
VISUAL TASK PERFORMANCE

This chapter is concerned with the relationship of vision to the performance of everyday life and work tasks. In approaching the question of how to determine if a worker has a disability for visual reasons the Social Security Administration (SSA) currently relies primarily on tests of basic, objectively testable visual functions— namely, acuity and visual fields—with the implicit assumption that these measures can predict ability to perform visually intensive work and daily life tasks. As understanding of the complexity of the relationship between the traditional measures of visual function and an individual’s actual abilities to perform important tasks has grown, SSA has become concerned about the predictive validity of such tests and specifically requested the committee to explore the possibility of using measures that more directly test the ability to perform daily life and work tasks.

The use of such measures would be contingent on meeting several challenges. First is the need to select a manageable set of surrogate tasks that adequately represent important vision-related tasks of everyday life and work. Second, SSA would have to ensure that tests of such tasks proposed for use in disability determination demonstrate construct validity and are reliable and well normed. The tests also



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Visual Impairments: Determining Eligibility for Social Security Benefits 3 VISUAL TASK PERFORMANCE This chapter is concerned with the relationship of vision to the performance of everyday life and work tasks. In approaching the question of how to determine if a worker has a disability for visual reasons the Social Security Administration (SSA) currently relies primarily on tests of basic, objectively testable visual functions— namely, acuity and visual fields—with the implicit assumption that these measures can predict ability to perform visually intensive work and daily life tasks. As understanding of the complexity of the relationship between the traditional measures of visual function and an individual’s actual abilities to perform important tasks has grown, SSA has become concerned about the predictive validity of such tests and specifically requested the committee to explore the possibility of using measures that more directly test the ability to perform daily life and work tasks. The use of such measures would be contingent on meeting several challenges. First is the need to select a manageable set of surrogate tasks that adequately represent important vision-related tasks of everyday life and work. Second, SSA would have to ensure that tests of such tasks proposed for use in disability determination demonstrate construct validity and are reliable and well normed. The tests also

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Visual Impairments: Determining Eligibility for Social Security Benefits must show a robust relationship to the requirements of jobs in the U.S. economy (i.e., must demonstrate strong predictive validity) as demonstrated in rigorous peer-reviewed research. The development of such tests is thus dependent on knowledge of the vision-related task requirements of the immense variety of jobs in the economy—jobs that are not stable but change over time. The committee conducted several interrelated inquiries in its effort to assess (1) the relationships between visual function measures and performance of everyday life and job tasks and (2) the possibility of using tests of vision-related tasks in disability determination. First, an iterative process was used to select a limited number of task domains to represent the broad range of vision-related everyday life and work tasks. Many candidate task domains were discussed, and a short list was developed, based on the collective expertise of committee members. In a concurrent effort described below, the relationships of the most common standard vision measures to actual performance on various jobs and tasks were analyzed. The information gathered in this review, when fed back to the selection of task domains, supported the committee’s selection of four task domains as representative and inclusive of the important tasks of everyday life and work: reading and related close work, such as use of a computer display, mobility, both ambulatory and driving, social participation, and tool use and manipulative tasks. The committee sought evidence to demonstrate (through both direct observation and self-report) the nature of the relationships between visual function measures such as acuity, visual fields, contrast sensitivity, and others and the actual ability of individuals in a community setting to perform important daily life tasks and other vision-related tasks that would be of importance in a job setting. Such evidence would scientifically support the claim that the testing of visual functions can predict job performance abilities—a predictive relationship that has not to our knowledge been rigorously demonstrated for the tests now used by SSA. We surveyed and

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Visual Impairments: Determining Eligibility for Social Security Benefits evaluated the experimental literature on these relationships. In addition, we conducted a concurrent literature review and analysis of the relationship of the vision measures now used by SSA—visual acuity and visual field loss—to individual self-reported functioning and health-related quality of life (HRQOL), in part because SSA requested that we evaluate the usefulness of HRQOL measures in disability determination methodology. This work provided valuable information for the committee’s task domain selection. An important goal of this work was to characterize the form of any relationships that were found between specific vision test results and task performance. For example, is there a step function or threshold in acuity or visual field scores at which performance on particular tasks deteriorates significantly, or is the relationship relatively continuous and uninflected, meaning that a “natural” cutoff point for disability could not be derived from the relationship? Finally, we assessed job analysis databases, two of them in depth, to determine the availability and quality of information about how important vision functions are related to the performance of job tasks, using current Department of Labor job taxonomies. In addition, we analyzed the importance of vision to specific job tasks or skills independent of the job categories. This effort was designed to evaluate the evidence available to support more specific and tailored job disability assessments that would require determination of which visual measures should be weighed in determining vision-related disability for specific job categories and the underlying job tasks in each category. This chapter discusses the committee’s findings from this set of investigations and analyses. First we present the findings on the importance and relationships to visual functions of each of the four task domains: reading, mobility, social participation, and tool use and manipulative tasks. These sections include reviews of available tests for these task domains and recommendations on the use of such tests for disability determination. Next we present findings on health-related quality of life measures, followed by a review of the evidence from occupational analysis databases. Finally, we summarize our recommendations regarding use of tests of visual task performance in disability determinations.

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Visual Impairments: Determining Eligibility for Social Security Benefits READING Description The Case for Including Reading Performance in Disability Determination Disability is one of the four levels of evaluation in the widely used classification of vision outlined by Colenbrander (International Society for Low Vision Research and Rehabilitation, 1999): disorder, impairment, disability, and handicap. Reading difficulty is the primary exemplar of a disability. Reading is a skill or ability possessed by a person rather than a characteristic of an eye or visual system per se. Like other important abilities of daily life, reading performance depends in complex ways on the interaction of visual input, cognitive proficiency, oculomotor control, and probably other factors. Two people with identical eye disorders and levels of impairment (as measured by such clinical tests as acuity) might easily perform differently in reading. The same person with no change in eye disorder or measured impairment might improve his or her reading performance as a result of rehabilitation. Reading also differs from clinical tests of visual impairment in being dynamic in character. Reading, like driving and hand-eye coordination, involves rapid visual information processing and online integration of vision with other processes. As described below, impairments in acuity, contrast sensitivity, and field status (especially central field loss) affect reading performance in characteristic ways, but they do not provide accurate predictions of reading ability. Agencies concerned with assessing disability in relation to work seek to determine whether individuals possess the capacities or skills to perform jobs. If reading is essential for a job, then a necessary condition for employment is the ability to read, with measured values of acuity or field being of only indirect relevance. Since reading is an essential component of many jobs in the modern American economy, a person with reduced reading ability is certainly disadvantaged. In this case, direct measurement of reading performance would be valuable in disability determination.

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Visual Impairments: Determining Eligibility for Social Security Benefits Reading is only one of many possible skills that might figure in disability assessment. How important is reading? Throughout the world, reading is one of the most highly valued activities in human culture. The United Nations and other international bodies use literacy rates as one of the primary indicators of social and economic development. To quote from Hamadache (1990): “The struggle for literacy is also a struggle for justice, for access to knowledge, and for equality. Literacy is an essential precondition for the effective exercise of human rights.” When eye disorders deprive or limit people’s access to the printed word, the issue is vision disability, not literacy, but the individual consequences may be just as severe. Because of the fundamental importance of reading, low vision is sometimes defined as the inability to read a newspaper at a normal distance with best correction (glasses or contact lenses). Reading difficulty is often cited as the most common presenting symptom in low vision clinics. For instance, Elliott et al. (1997) reported that reading was the primary objective for 75 percent of elderly patients seeking low vision rehabilitation and the secondary objective for 21 percent. Leat et al. (1999) reported that surveyed patients had a priority for reading medicine bottles and bank statements over reading the newspaper. During the public forum held by the committee as part of its information-gathering activities, most of the presenters noted the limitations of impairment measures for assessing disability in skills of daily life, including reading. This concern with reading is consistent with our analysis, based on the Position Analysis Questionnaire, a proprietary job analysis system, that indicated that written communication is important in 47 percent of jobs. Given the importance of reading to employment and other activities of daily life and the imprecision of estimating reading disability from traditional measures of visual impairment, a strong case can be made for including evaluation of reading performance in disability assessment. As described below, although reading performance is related to measures of visual impairment (acuity, contrast sensitivity, and field), a direct measurement of reading performance on a well-

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Visual Impairments: Determining Eligibility for Social Security Benefits standardized test would provide additional information that may be relevant to disability determination. Before presenting a recommendation about the inclusion of a test of reading in disability assessment, we address several questions: What is the range of reading tasks under consideration? What aspects of reading have been measured? What clinical tests of reading vision already exist? What are the desirable characteristics of a suitable reading test for disability assessment? After addressing these questions, we turn to an evaluation of reading tests for assessing disability. The Range of Reading Tasks Reading is a cluster of different tasks that impose different demands on vision, motor control and language skills. In conventional reading, people navigate through the text with a series of brief eye movements called saccades, separated by pauses called fixations. People with mild to moderate visual impairment may use optical magnifiers, requiring coordination of hand movements, head movements, and eye movements. People with more severe visual impairment may use electronic magnifiers such as closed circuit TV. There is a trade-off between the amount of magnification and the proportion of a printed page that is visible in the magnifier’s field of view. Two problems result from the restricted field. First, there is the question of the number of letters in the field (window size) necessary to support the fastest reading. The critical number is at least four and can be greater, depending on the motor demands for magnifier scanning (cf. Beckmann & Legge, 1996; Legge, Pelli, et al., 1985). Second, the diminished field seen through the magnifier hides the global layout information on the page (Den Brinker & Beek, 1996). Knowledge of the global layout of text is not very important for the sequential line-by-line reading of continuous prose. But nonsequential reading occurs in skimming text for gist or searching text for critical terms or hyperlinks. While the impacts of magnification and field size are fairly well understood for sequential text reading, relatively little is known about their impact on nonsequential reading.

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Visual Impairments: Determining Eligibility for Social Security Benefits Nonsequential reading is taking on greater importance with the growing use of computers at work and in the home. Screen magnification on computers has been implemented in commercially available software applications. Although these forms of adaptive technology have proven remarkably useful, they have generated new problems in dealing with the nonsequential display of information on computers.1 It is expected that the growing use of hypertext in computer reading and increased reliance on graphical displays (typically nonsequential in their use) will impose extra burdens on reading by people with disabilities. This is an area in need of research. It should also be noted that researchers have experimented with nontraditional methods for displaying text in hopes of finding a method particularly advantageous for people with low vision. For instance, the RSVP method (rapid serial visual presentation), involves displaying words of a text sequentially at the same place on a display screen, minimizing the need for eye movements. People with normal vision can read RSVP text much faster than conventional text (Rubin & Turano, 1992). Despite high hopes for a similar improvement in speed for people with low vision, RSVP provides only a modest benefit for readers with low vision (Fine & Peli, 1995; Harland et al., 1998; Rubin & Turano, 1994). A variant of RSVP, called ESP (elicited sequential presentation) provides a modest benefit in reading speed (Arditi, 1999). One disadvantage of RSVP and ESP is that they do away with global layout information altogether. Reading in the real world is not restricted to books, sheets of paper, and computer screens. Signage is important for mobility, both walking and driving. Spectacle-mounted or hand-held telescopes can be useful for finding signs, but the targeting process is time-consuming and is difficult to accomplish while the viewer is in motion. Stabilization of features in the magnified retinal image requires recalibration of the relationship 1   Here are two examples. Imagine that the lower right quadrant of a computer screen is magnified so that it fills a low vision user’s computer display. Activity outside this quadrant, such as menus, prompts or error messages, will simply not appear on the screen. Next, imagine using a screen magnifier to move through text with scroll bars. Either the text of interest or the scroll bars will be visible in the magnified view, but not both at the same time.

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Visual Impairments: Determining Eligibility for Social Security Benefits between head movements and compensatory eye movements, known as the visual vestibulo-ocular reflex (Demer et al., 1988). In short, while telescopes can be used for reading and other high-acuity distance tasks, there are serious practical limitations. Other common reading tasks in the workplace include monitoring of dials and instrument panels, retail labels, and financial documents, including currency notes (National Materials Advisory Board & National Research Council, 1995). It is important to keep in mind that many visually disabled people use nonvisual methods for reading in addition to or instead of print. Text can be read aloud by live assistants or recorded on audio tape. Digital documents can be spoken by speech synthesizers. With the advent of optical scanning, improved speech-recognition software, and the widespread creation of electronic documents, computer-based speech has become a realistic option for both vocational and pleasure reading. This technology has reduced the dependence of visually disabled readers on sighted assistants. It should be noted, however, that the sequential nature of auditory displays makes nonsequential text reading difficult. Some screen reader programs (such as JAWS by Freedom Scientific) have included special functions to help with nonsequential reading (e.g., a function that groups all hyperlinks on a web page into a single column). Between 15,000 and 85,000 Americans use Braille (Legge et al., 1999). Although Braille reading speeds average about a factor of two lower than print reading speeds, Braille is especially valuable in contexts in which magnifiers or auditory displays are inconvenient. Word processing documents can be converted to Braille codes by software and embossed on Braille printers. Braille note takers (for example, Braille ‘n Speak by Freedom Scientific or BrailleNote by PulseData) permit users to type Braille on a compact keyboard for later reproduction by synthetic speech, print, or embossed Braille. There is a debate over the mode of instruction for teaching visually impaired children to read—print, Braille, or tape. In one view, children with low vision should learn to read print because the majority of written material appears in print. In another view, children should learn to read Braille because it is often more

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Visual Impairments: Determining Eligibility for Social Security Benefits convenient than reading with a magnifier, and because it is hard to learn later in life when vision may decrease further. Almost everyone agrees that strict reliance on audio recordings is undesirable because it results in poor spelling and even illiteracy. Measuring Reading Reading performance has been evaluated in many ways. A brief review follows. Clinical tests of reading are discussed in the next section. Reading Acuity and Critical Print Size. Reading acuity refers to the measurement of visual acuity using a test chart containing paragraphs, sentences, or words in typeset print. The test material for reading acuity is more congested and complex than the letter chart, which has relatively widely separated letters. Not only is the reading material more crowded, but there is more spatial integration required to correctly recognize individual words and word strings. Reading acuity is highly correlated with letter acuity, although some people with low vision, particularly those with macular degeneration, have poorer reading acuity than letter chart acuity (Lovie-Kitchin & Bailey, 1981). Reading acuity is typically measured at a near viewing distance such as 40 cm. Newsprint, held at a distance of 40 cm (16 inches), would typically be at the limit of resolution of someone with reading acuity of 20/50. Accordingly, someone with a reading acuity poorer than 20/60 (a common definition of low vision) would be unable to read newsprint without bringing the page closer to the eye or using some other form of magnification. A newer concept is critical print size. While reading acuity documents the angular size of the smallest print size for which reading is possible, a somewhat larger print size is required for fluent, effective reading. For a given viewing distance, the critical print size, two or more times larger than acuity letters, is the print size beyond which the size of characters no longer inhibits reading performance. Although optical and closed circuit television magnifiers are often prescribed to magnify selected specimens of printed material to achieve the observer’s critical

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Visual Impairments: Determining Eligibility for Social Security Benefits print size, it is only recently that critical print size has received attention from researchers. For example, consider a person with 20/200 reading acuity whose critical print size is 3 times larger than their acuity limit. If 4-fold magnification brings typical newsprint to this person’s acuity limit, then 12-fold magnification would be necessary to reach the critical print size for effective reading. Although 4-fold magnification might be easily accomplished with a hand-held optical magnifier, 12-fold magnification could require a more specialized magnifying device and a smaller field of view. The important point is that the nature of the prescribed magnifier, as well as the functional outcome, may depend on whether text letters are enlarged to the acuity limit, to the critical print size, or to an intermediate size. DeMarco & Massof (1997) have surveyed the distribution of print sizes in 10 different sections of 100 U.S. newspapers. Median print sizes range from M = 0.78 (stock listings) to M = 1.21 (comic strips), corresponding to Snellen sizes (at 40 cm) of 20/40 to 20/60. (M-units indicate the distance in meters at which the letter height subtends 5 minutes of arc. For example, 1.0 M print subtends 5 minutes at a distance of 1 meter and is 1.45 mm high.) Anyone with a critical print size larger than 20/60 would be at a disadvantage in reading text similar to newspapers at a distance of 40 cm. At that distance, they would either read slowly (if at all) or would require some magnification. Reading acuity and critical print size are familiar measures to eye care professionals because of their similarity to letter acuity. The following measures are less familiar and have been used more in rehabilitation or research contexts. Reading Speed. Reading speed, in words per minute (wpm), has been widely used in psychophysical studies because it can be measured objectively, is reproducible, and is sensitive to variations in visual parameters (Carver, 1990; Legge, Pelli, et al., 1985; Tinker, 1963). Reading speed is a measure that reflects the dynamic nature of reading. One problem with this measure is that reading speed depends on the difficulty level of the reading material. Factors such as the component words, the sentence structure, and the simplicity or complexity of the content necessarily cause variations in difficulty

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Visual Impairments: Determining Eligibility for Social Security Benefits from one passage to the next or from one observer to another. Mean word length varies from passage to passage, increasing with text difficulty. Carver (1990) has shown that differences in speed due to text difficulty can be reduced by measuring reading speed in “standard-length words” per minute, wherein each six characters count as one standard-length word. Carver has shown that, on average, a subject’s reading speed is about constant in standard-length wpm across text difficulty, provided the grade level of the text does not exceed the reading level of the subject. Average prose reading speed in English for normally sighted adults is about 250 wpm (cf. Legge et al., 1999). Whittaker & Lovie-Kitchin (1993) have identified three slower rates, based on clinical experience, associated with different levels of function in people with low vision: (1) spot reading (44 wpm), adequate for many tasks of daily life, such as reading mail, recipes, and labels; (2) fluent reading (88 wpm), and (3) high fluent reading (176 wpm). Note that their high fluent rate is well below the typically cited mean value for normally sighted reading speed. A sustainable reading speed of 176 wpm, while still slow for a normally sighted reader, would probably be adequate for meeting the needs of all but the most reading-intensive jobs. However, a person whose maximum reading speed is 90 wpm or less is functionally disadvantaged in reading, lying more than two standard deviations below the normal mean (Legge et al., 1992). Accuracy. The percentage of words read aloud correctly is sometimes used, especially in cases in which it is expected that faulty control of eye movement may lead to missed portions of text or if the person is inclined to guess. Endurance. Sometimes people with low vision can read rapidly for a short period, but the motor demands of a magnifier or the nature of the eye condition precludes lengthy sustained reading. There has been little study of reading endurance, but it is surely an important issue for some types of work. Comprehension. Comprehension is tested in many cognitive and educational studies of reading. Standardized tests, such as the SAT or GRE, evaluate comprehension. It appears that comprehension is not much affected by eye condition or a person’s maximum reading speed

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Visual Impairments: Determining Eligibility for Social Security Benefits Department of Labor Occupational Information Network A second database examined by the committee is the Occupational Information Network (O*NET) system, which provides an online, comprehensive, interactive database system of job descriptions developed by the Employment and Training Administration (ETA) of the U.S. Department of Labor (DOL). The original database used in O*NET 98 (subsequently refined and updated) is based largely on data supplied and refined by occupational analysts from sources such as the Dictionary of Occupational Titles (DOT) (U.S. Employment Service, 1991). Groups of five or six occupational analysts and graduate students in industrial and organizational psychology, working independently, rated each of the occupations using the appropriate survey. O*NET is intended to replace the existing Dictionary of Occupational Titles. The operational model of O*NET is the Content Model, which includes a questionnaire divided into six sections that represent the major elements for categorizing and classifying job information. The six areas of the Content Model, the characteristics on which each job is rated, are: (1) worker characteristics, (2) worker requirements, (3) occupation requirements, (4) experience requirements, (5) occupation-specific requirements, and (6) occupation characteristics. Under worker characteristics is the category sensory abilities. Under sensory abilities are located seven visual abilities: near vision, far vision, visual color discrimination, night vision, peripheral vision, depth perception, and glare sensitivity (Hubbard et al., 2000). While the structure is promising, O*NET analysis is not yet able to provide meaningful analysis of jobs by worker characteristics. Furthermore, the current O*NET database is not yet a representative sample of the U.S. working population and has not yet been widely used. Usability of the PAQ Database The PAQ database includes 2,523 job titles with specific ratings. Each job was assigned to one of the nine DOL aggregate job categories, such as clerical or agriculture and fisheries. On the basis of these nine

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Visual Impairments: Determining Eligibility for Social Security Benefits larger groupings, the PAQ database was adjusted to be proportional to the distribution of the employed adults in the United States as of 1993. This was accomplished through a weighting of responses to reflect data from the DOL, using the first digit of the DOT code (McCormick et al., 1998b). Therefore, if 3 percent of the jobs were in agriculture and fisheries, then 3 percent of the jobs in the database are in agriculture and fisheries. The PAQ assesses jobs and not the people holding jobs. In assessing how codes were developed and assigned, our analysis revealed that there are 1,817 unique DOT job codes and the rest are overlapping codes, with data created using a bootstrap technique to take all the persons who responded within that job code and create another entry for that job code, to arrive at the number of 2,523. For each job title, there may have been anywhere from one to several hundred measurement sessions. For each measurement session, there may be one or more observations by different persons (job incumbent, supervisors, consultants, analysts). Because of the proprietary nature of this database, the committee could not determine how many job title assessments are based on only one or very few respondents. It was reported by the developers of the PAQ (Richard Jeanneret, personal communication) that the number is very small. The response in the database for each job title is the average response for all persons who analyzed that job title (thus, the average reponses may include decimals, although the input responses are integers). There are additional significant limitations in the potential generalizability of the PAQ analysis results. First, the data collected do not arise from a random sample of jobs within each of the 1,817 unique job titles or the nine aggregate categories. Second, and even more importantly, among individuals with specific jobs, the selection of the sample may not be representative of all persons holding that specific job. Furthermore, the responses for each specific job are aggregated over time, starting from the 1970s. As a result, there may be potential biases from changes in jobs that occur over time for which the ratings have not sufficiently reflected the new methods and concerns. This is of particular concern given the averaging of all responses over the past 30 years. For example, 30 years ago, the use of “hand-held control devices” encompassed very different tasks than it

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Visual Impairments: Determining Eligibility for Social Security Benefits does today, when the use of a computer mouse and other such input devices is included in this category. Similarly, 30 years ago, before computers were common on office desks, most managers would not have reported much use of keyboards. Other limitations to the PAQ database are inherent in the method of data collection by multiple observers. Individuals who perform the job, their supervisors, and experts in the field may each rate the job. Ratings may therefore vary with individual interpretations of the standards used for the ratings, with raters’ understanding of the visual functions they are rating, and with the raters’ depth of knowledge of the job’s requirements. Despite these limitations, we did not identify a comparable or better data structure for job analyses in the United States. The validity of the PAQ system has been tested over 30 years by the employer and business communities, which use its results for employment and planning purposes. Reliability ratings suggest that the PAQ has reasonable interrater and test-retest performance (McCormick et al., 1998a). The unique benefits of the PAQ system suggest that it may be used carefully to augment our understanding of vision and vision decrements in the workplace, despite its proprietary nature and the lack of previous use for these purposes. The PAQ instrument gathers information on the following visual and perceptual characteristics of jobs: near visual acuity, far visual acuity, depth perception, and color discrimination. It does not include assessments of visual field or contrast sensitivity. Furthermore, it measures near vision differently than the other three variables (see below). Nevertheless, it is possible to enter the database and examine the visual demands in one or all of these categories for specific jobs, job families or categories, or broad occupational groupings. And it is possible to concentrate on the specific visual demands of particular tasks within or across jobs (e.g., the use of hand-held tools, the manipulation of fixed or variable controls, assembly or disassembly tasks). However, because of the data source limitations noted above, the committee chose to use analyses limited only to the nine

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Visual Impairments: Determining Eligibility for Social Security Benefits TABLE 3-1 Ratings of the Importance to the Job of Aspects of Vision (percentage) Level of Importance Near Acuity Far Acuity Depth Perception Color Perception Does not apply 0.5 38.1 46.6 47.3 Very minor 3.0 23.0 24.2 24.6 Low 17.6 19.6 14.6 13.9 Moderate 69.2 13.2 9.8 9.1 High 8.8 5.2 4.1 3.8 Extreme 0.9 1.0 0.8 1.3   Source: Position Analysis Questionnaire database of 2,523 job title ratings. aggregate DOL levels and not to use results from variation at the individual job title level. The PAQ was thus used to determine how important vision is to job category performance in the aggregate and across the nine standard DOL job categories. The first analysis is the distribution of responses to the four main vision items. Respondents were asked to rate the importance to their job of far acuity (defined as differences in seeing characteristics beyond arm’s reach), near acuity (defined as the amount of detail that must be seen within arm’s reach), depth perception (defined as judging the distances between objects), and color perception (defined as differentiating objects or details on the basis of color). As the definitions were worded, only the response for near acuity captures “blind or working in darkness” at the zero end of the scale; the rest of the vision categories score “0” as “does not apply.” Therefore, the distribution for near acuity is much less skewed than for the other vision variables. As seen in Table 3-1, for the distribution of job titles in the database, far acuity, depth perception, and color perception are of low or minor importance—or do not apply—to 80 percent or more of respondents. However, 69 percent of the respondents rated near acuity as of moderate importance, with 10 percent rating it as of high or extreme importance. While it is clear that the distributions are sensitive to the

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Visual Impairments: Determining Eligibility for Social Security Benefits structure of the response choices, it is also apparent that the respondents placed considerable importance on near acuity for job performance. The second analysis is the distribution of responses indicating the importance of four main vision items according to the nine major job categories (Table 3-2). The levels are numerically coded as <3 = low or minor importance; 3 = moderate importance; 4 = high importance; TABLE 3-2 Rating of the Importance of Vision to Job Performance by Broad Category of Job (percentage) Vision Importance Prof/Tech Clerical Service Ag/Fish Near Acuity Not Applicable to Low 11 14 45 51 Moderate 77 82 46 49 High 11 4 8 0 Extreme 1 0 1 0 Far Acuity Not Applicable to Low 84 93 69 52 Moderate 11 4 23 24 High 4 3 5 19 Extreme 1 0 2 5 Depth Perception Not Applicable to Low 88 98 82 61 Moderate 8 2 13 25 High 4 1 3 11 Extreme 0 0 1 3 Color Perception Not Applicable to Low 87 94 80 89 Moderate 9 4 12 11 High 3 2 7 0 Extreme 1 1 1 0 (N) 737 707 352 75   Source: Position Analysis Questionnaire database of 2,523 job title ratings.

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Visual Impairments: Determining Eligibility for Social Security Benefits 5 = extreme importance. Differences by category are apparent. Service jobs and agricultural/fisheries jobs do not rate near acuity as important as do the professional/technical and clerical and sales jobs. However, depth perception is rated more important for jobs in agriculture/fisheries and benchwork, compared with professional and clerical jobs. There is uniformity in the low rating given to the importance of color vision across jobs. Process Machine/Trades Bench-work Structural Misc.   36 19 12 17 42 57 67 63 69 46 5 13 22 12 11 2 1 3 2 1   68 78 90 67 56 26 16 9 20 26 5 6 1 13 16 1 0 0 1 2   77 74 72 69 73 17 19 14 22 15 5 6 10 8 9 1 1 4 1 3   82 83 72 75 77 12 11 16 17 16 6 5 7 6 6 1 2 5 2 2 139 191 105 87 110

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Visual Impairments: Determining Eligibility for Social Security Benefits Conclusions The committee sought to determine if empirical data existed to help understand the relationship between visual skills and abilities and workplace performance and job requirements. Two datasets were identified as being potentially useful. The first, O*NET, was determined to not yet be a representative nor usable data source at this time, although it may become so in the future. The second, the PAQ, was judged to provide information that would otherwise be unavailable. With the appropriate understanding of the limitation of the PAQ database design, its limitations in execution, and the weighted nature of the data, the PAQ provides information of an otherwise inaccessible nature and was thus used as presented by the committee in a limited fashion. The key limitations of the database reflect in part its proprietary nature and include the following: Representativeness of the U.S. job market (not people) exists only at the aggregate nine-category level, not for any of the 2,523 specific job titles nor across the aggregate of job titles; Each of the 2,523 job titles has an unknown number of measurement sessions and an unknown number of observations per measurement session; The cumulative measurements for each job title are averaged over a 30-year time period and thus may not fully capture changes in workplace requirements as job functions change over time; The PAQ was intended to be used for other purposes than the one the committee is undertaking; The vision variables are limited (no contrast sensitivity and no visual field items) and the near vision variable is measured differently from far vision, color, or depth perception. The results of our analyses demonstrate that facets of vision remain important to many jobs across the range of job titles or the nine aggregate DOL categories. They also demonstrate, however, that the

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Visual Impairments: Determining Eligibility for Social Security Benefits importance of vision and of the four measures of visual function being rated—near acuity, far acuity, color, and depth perception—vary across the job categories and specific work or job skills. Because of concerns about the data, we have chosen to limit the analyses to no more detail than the nine categories. We make the following specific points: Analyses of the PAQ database demonstrate that near visual acuity is rated to be of high or extreme importance in 9.7 percent of 2,523 job titles, while far acuity is of similar import in 6.2 percent, depth perception in 4.9 percent, and color perception in 4.1 percent. An additional 69.2 percent of job ratings place near acuity as of moderate importance, while only 13.2 percent so rate far acuity, 9.8 percent depth perception, and 9.1 percent color perception. Thus, the importance of focusing more attention on near acuity assessment for disability determination is suggested. At the same time, the weight to be given to near acuity or to the other vision variables should vary depending on the sector of the economy (i.e., job classification) in question. While 89 percent of professional and technical job ratings indicate that near vision is of at least moderate importance, only 55 percent of service job ratings and 49 percent of agricultural or fisheries job ratings do so. In contrast, 48 percent of agricultural or fisheries job ratings indicate that distance acuity is of at least moderate importance, while only 7 percent of clerical jobs rate it that highly. Depth perception is commonly rated of at least moderate importance only in agricultural and fishing jobs (39 percent) and least important in the clerical sector job ratings (2 percent). Finally, color is most important to the benchwork (28 percent of ratings) and structural (25 percent of ratings) job ratings and least important in the clerical (6 percent). When analyzed by specific job skills relative to each of the nine DOL categories and each of the vision variables, each of these two earlier patterns is seen again. Thus, vision remains relatively important for most job skills, although there is some variation across labor categories and the specific visual task varies by job skill even within the same labor category.

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Visual Impairments: Determining Eligibility for Social Security Benefits RECOMMENDATIONS FOR TESTS OF VISUAL TASK PERFORMANCE The committee’s review of the potential for using tests of performance of vision-related tasks determined that for most of the task domains we examined, SSA should not attempt to test performance as a part of its disability determination process, using the tests now available. The one important exception is for reading. The committee also determined that health-related quality of life measures, although useful as indicators of important tasks and activities of daily life that are affected by vision loss, are not appropriate as tests for use in disability determination. The specific recommendations are presented below. Reading The committee recommends that a test of reading should be included in the vocational factors steps (Steps 4 and 5) of the disability determination process as soon as a well-normed reading test can be shown to meet test standards to be established by SSA. Reading tests are available that should be able to meet such criteria after modest additional research and development efforts, and we recommend that SSA support such research. We recommend the following criteria for reading tests: Visual characteristics that are consistent with contemporary standards for acuity tests, including a logarithmic progression of print sizes; A range of print sizes containing large enough print to be useful with most visually impaired people and small enough print to reliably measure reading acuity in normally sighted people; Text passages equated in layout across print sizes; Reproducible rules for estimating reading acuity, critical print size, and reading speed;

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Visual Impairments: Determining Eligibility for Social Security Benefits Binocular testing, unless one eye interferes with the other in reading and the problem can be addressed by covering the interfering eye; and Text passages representative in font and letter spacing of commonly encountered real-world texts. We recommend additional research to establish in more detail the distributions of reading acuity, critical print size, and reading speed in different age groups, and the relationships between these measures and performance of work-related activities and the instrumental activities of daily life. Mobility The committee recommends no testing of ambulatory or driving mobility at this time. The evidence suggests that most ambulatory mobility problems will be captured by tests of visual functions: contrast sensitivity, visual fields, and acuity. The committee recommends that mobility problems related to other functions not tested (glare, light adaptation, binocularity, or visuocognitive problems) should be subjectively evaluated for their disabling impact, pending development of acceptable tests of such functions. For driving mobility, although we recommend no task-based testing at this time, the committee recommends that SSA support development of tests of more complex visual functions that have been shown to affect driving safety, such as divided attention and visual processing speed. Tool Use and Manipulation The committee recommends no testing of tool use tasks directly at this time, but we do recommend that SSA support research into adapting commonly used industrial tests that involve tool use for future application to detection of vision-related disability.

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Visual Impairments: Determining Eligibility for Social Security Benefits Social Participation The committee recommends no use of any instrument currently available to test the impact of vision loss on social participation. Current research measures, such as tests of face recognition, are not appropriate for such use. Tests of visual acuity and contrast sensitivity should capture some of the relevant disability in social participation. Tests of social participation should not have high priority at this time, although they may merit reconsideration in the future. Health-Related Quality of Life The committee’s examination of HRQOL instruments indicates that these instruments can provide valuable information for the assessment of the general relationships of visual impairments to functional disability, but they are not likely to be useful as tests for determining disability in individual claimants. A major weakness is that the instruments rely on self-report of functional status and are thus subject to gaming by claimants motivated to demonstrate loss of function in order to qualify for benefits.