1
INTRODUCTION

The problem of visual loss is recognized as a significant issue by the American public. The federal government recognized the potential disability associated with visual loss when it incorporated Aid to the Blind into the Social Security Act of 1935 (Koestler, 1976, p.45). Thus, the issue of the appropriate determination of disability for individuals with visual impairment is an important one for the Social Security Administration (SSA).

This report assesses the existing disability determination process used by SSA to identify individuals with visual impairments in the context of current scientific knowledge and clinical practice. The charge of the Committee on Disability Determination for Individuals with Visual Impairments was to:

  • Evaluate current scientific understanding of the visual demands of everyday tasks, including information that can be obtained from quality-of-life measures.

  • Examine the adequacy of the current tests of central visual acuity and visual field as measures of the capacity to work.



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Visual Impairments: Determining Eligibility for Social Security Benefits 1 INTRODUCTION The problem of visual loss is recognized as a significant issue by the American public. The federal government recognized the potential disability associated with visual loss when it incorporated Aid to the Blind into the Social Security Act of 1935 (Koestler, 1976, p.45). Thus, the issue of the appropriate determination of disability for individuals with visual impairment is an important one for the Social Security Administration (SSA). This report assesses the existing disability determination process used by SSA to identify individuals with visual impairments in the context of current scientific knowledge and clinical practice. The charge of the Committee on Disability Determination for Individuals with Visual Impairments was to: Evaluate current scientific understanding of the visual demands of everyday tasks, including information that can be obtained from quality-of-life measures. Examine the adequacy of the current tests of central visual acuity and visual field as measures of the capacity to work.

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Visual Impairments: Determining Eligibility for Social Security Benefits Explore other existing tests of visual function as means of simply and reliably estimating visual capacity, alone or in combination with other tests. Examine the potential value of new measures and procedures for estimating visual disability. Identify where more work might be required to better characterize visual impairments, to better estimate functional capacity, and to better characterize the visual requirements of work and everyday tasks. This report is the committee’s response to these challenges. ISSUES THAT PROMPTED THE STUDY SSA administers benefits programs for people with long-lasting disabilities that severely affect their ability to work or, for children, to perform everyday activities like their peers. Under Title II of the Social Security Act, workers covered by Social Security may qualify for benefits called Social Security Disability Insurance (SSDI, often referred to as DI). Under Title XVI, adults and children who are not eligible for DI may qualify for Supplemental Security Income (SSI) benefits, which are means-tested disability benefits. For each person who comes to SSA to request disability benefits (formally referred to as a “claimant”), SSA must determine whether he or she is eligible under the program regulations that implement the laws Congress has enacted for Social Security disability benefits. SSA was concerned that, while its criteria are intended to identify claimants whose visual impairment severely reduces their ability to work, the agency has little information about the relationship between performance on medical tests of vision and performance of vision-dependent tasks on the job. The SSA Office of Disability is also aware that the criteria it uses are based on old medical practices and that new and refined methods of testing visual function are being used in the medical and rehabilitation communities.

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Visual Impairments: Determining Eligibility for Social Security Benefits Predicting Performance in the Workplace The overall goal of disability assessment is to establish functional capacity (fitness for work). The committee examined how best to do that, whether through the use of simple tests of visual function, such as acuity and visual fields, or through testing more complex, visually dependent skills, such as reading and driving, or even through the direct measurement of visual performance in the workplace. A good deal is now known about the visual requirements of work-related tasks like reading and mobility, as well as about the visual capabilities most missed by people with impaired vision. Much work has also been done to assess the impact of different degrees of visual impairment on a person’s quality of life, by using questionnaires and by observation of behavior in different everyday contexts. Although the measurement of overall performance has been a major focus of research on people with low vision and has become central to the assessment of disability in children (discussed below), it has not been systematically examined as a means of assessing visual disability in adults. Adequacy of Current Tests The SSA disability determination process uses basic tests of visual acuity and visual fields that were standardized in the 1950s. The SSA regulations specify quite precisely some conditions under which tests should be administered but provide little guidance on others, particularly those for the measurement of acuity. Understanding of what the tests measure has advanced greatly since the SSA regulations were formulated, and the instruments used for measurement have been much improved, offering the prospect of more refined and reliable assessment. Recognizing this, in 1994 SSA sought advice from the National Research Council’s Committee on Vision on the testing and scoring procedures that should be used to obtain reliable measures of central visual acuity and visual fields. The resulting report (National Research Council,

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Visual Impairments: Determining Eligibility for Social Security Benefits 1994) noted that the current standards have important weaknesses, in addition to making recommendations about how tests should be administered in ways that conform to the standards. That report served as a point of departure for the current study, and its findings informed our investigation of visual disability determination methods. Limited Range of Visual Functions Tested The tests of central visual acuity and visual fields described in SSA’s medical listings assess key aspects of visual performance, but they do not touch on other dimensions of vision that may be relevant to overall functioning in everyday life and the workplace. In its 1994 report, the Committee on Vision commented on some of these, which we mention here. An important element of normal vision is the capacity to distinguish small differences in the brightness of adjacent regions in a scene. The better one’s spatial contrast sensitivity, the better one can distinguish an object from similar surroundings, and the better one can distinguish fine detail. Contrast sensitivity has been studied systematically since the 1960s, and its potential importance in clinical assessment has only recently been recognized. Impaired contrast sensitivity can result in poor vision that is not readily detected by such measures as visual acuity. Other visual capabilities that are potentially important include binocular vision, which is the use of two eyes to provide normal vision. Disruptions of binocular vision can lead to double vision and impaired capacity to distinguish small differences in depth. The SSA criteria take no account of impairments of binocular vision other than those that might arise through paralysis of the eye muscles. Impairments of color vision, both congenital and acquired, are not uncommon, especially among males. These generally result in one’s being unable to distinguish colors that are readily distinguished by people with normal color vision. The SSA criteria take no account of the weaknesses of color vision, either as isolated impairments or in conjunction with others.

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Visual Impairments: Determining Eligibility for Social Security Benefits There are at least two issues related to the brightness or darkness of the environment in which a person is trying to see: adaptation and glare. The normal visual system is able to adjust its sensitivity rapidly (adapt), so that one can see well over the very wide range of light intensities encountered in normal life. Impairments of adaptation can leave one unable to see well at low or high light levels. The SSA criteria do not touch on impairments of light or dark adaptation. Light from a bright source in the field of view can be scattered within the eye. This scattering, known as glare, reduces the contrast in the retinal image. Some people are very susceptible to glare and their vision can be much impaired by it. The SSA criteria do not provide for the measurement of susceptibility to glare. Visual search is another aspect of visual function that may be important in everyday life and work. It allows one to locate and select objects of importance in the environment, in order to respond appropriately to them. This function is not now part of the testing for disability determination. PREVALENCE AND SIGNIFICANCE OF VISUAL IMPAIRMENTS Estimates of Visual Loss There are many different estimates of the number or prevalence rates of people in the United States with visual impairments, all supporting the assertion that this population is significant, is likely to be greater in underserved populations, and increases markedly with age. The variation among estimates is in part due to differences among the surveys in the assessment of vision (self-report of vision loss versus loss based on standard visual testing), differences in definitions of blindness and visual impairment, and differences in the age, socioeconomic status, and racial/ethnic mix of the populations studied. The committee reviewed several population-based studies that included detailed examination of visual status, not all of them based

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Visual Impairments: Determining Eligibility for Social Security Benefits on U.S. populations. They include the Baltimore Eye Survey (Rahmani et al., 1996; Tielsch et al., 1990), the Beaver Dam Eye Study (Klein et al., 1991), the Rotterdam Study (Klaver et al., 1998), the Blue Mountains Eye Study (Attebo et al., 1996), the SKI study (Brabyn et al., 2000), Proyecto VER, a study of Hispanic populations in Arizona (Munoz et al., 2002; Rodriguez et al., 2002) and the Salisbury Eye Evaluation Study (Rubin et al., 1997). Because visual loss is strongly dependent on age, most of these studies are based on older population samples, ranging from age 40 and older in the Baltimore study to age 65 and older in the Salisbury study. Each of these studies except one examined sample sizes of 2,500 or more subjects, with four each having over 4,000 subjects. Table 1-1 shows their reported rates for blindness and measured visual impairment, according to the study definitions. Rates cannot be directly compared, however, because the actual age structure may differ among study populations. The rates of blindness and visual impairment as reported in the age-specific analyses in these studies suggest that blacks and Hispanics have more vision loss than whites. The data are difficult to summarize for several reasons: the studies used different definitions of visual loss, the age distributions are different (e.g., the Hispanic population age 40 and older is much younger than other populations age 40 and older), some studies are decades older than others and are affected by the rise in the rate of cataract surgeries, and the age ranges vary from 40 and older to 65 and older. Overall, the prevalence of blindness varied from 0.3 percent in a population age 40 and older to greater than 1.7 percent in a black population age 65 and older. Blindness rates in the populations less than age 65 are unstable because vision loss is rare; most studies report rates of less than 0.3 percent. The studies in which detailed ophthalmological examinations have been carried out to determine causes of visual loss were most informative as to major causes of vision impairment in adults. These causes will change with age, as cataract, glaucoma, and age-related macular degeneration (AMD) assume more prominence in the older age groups. There are also shifting trends over time related to changes in medical practice, as cataract surgery has become more frequent in the past 15 years, leading to less cataract blindness and visual loss over time.

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Visual Impairments: Determining Eligibility for Social Security Benefits The ranking of causes is quite different in the 40 to 65 age group than in the older group, with AMD and cataract, disorders commonly related to age, accounting for much less of the total impairment in the younger age group. Diabetic retinopathy and other causes of visual loss were much more important at younger ages. AMD was the leading cause of blindness among whites, and cataract, glaucoma, and diabetic retinopathy the leading causes among blacks. For Hispanics, the leading cause of blindness was glaucoma; the leading cause of visual loss was cataract, followed by diabetic retinopathy and AMD. The committee recognizes that many people with visual impairments have other impairments as well. We considered this in our evaluation of tests, noting when particular tests require capabilities in addition to vision, such as motor skills or literacy. We have given the most attention to this issue in the discussion of tests for infants and children, for whom multiple impairments are especially important (Chapter 4). We have not, however, considered how the results of tests for visual impairments might be combined with those for other impairments to produce composite disability scores. This issue is beyond the scope of work the committee was asked to perform. Self-Reported Visual Problems In addition to actual ophthalmological determination of visual loss are people’s perceptions of visual problems and the self-reported impact on function that such problems may cause. Various health surveys have used different phrases, such as “cannot see at all,” when asking respondents whether they are blind. One estimate of the numbers of persons with disability due to self-reported visual impairments1 is based on the 1992 National Health Interview Survey 1   The committee prefers to use the term “impairment” only to refer to measured loss of visual function, and to refer to self-reported losses as vision “problems” or “limitations.” However, the NHIS questionnaire and datasets use the term “impairment” for such self-reported losses, so we have used it in that way in reference to NHIS data only.

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Visual Impairments: Determining Eligibility for Social Security Benefits TABLE 1-1 Rates of Visual Impairment (VI) and Blindness in Population-Based Studies Authors Population Beaver Dam White (one city in Wisconsin) Baltimore: White (inner city)   Black (inner city) Blue Mountain White (Australian city) Rotterdam White (one district in city, Holland) VER Hispanic (2 cities, Arizona) Salisbury Eye Evaluation White (city in Maryland)   Black (city in Maryland) *This definition of visual impairment is more lenient than that of the other studies; it includes those with acuity of 20/40, whereas others defined impairment as acuity worse than 20/40.

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Visual Impairments: Determining Eligibility for Social Security Benefits Age Range Definitions Data 43+ VI *: ≤20/40 Blind: ≤20/200 VI: 5.2% Blind:0.5% 40+ VI: <20/40 (white):2.2% (black): 3.9%   Blind: ≤20/200 (white): 0.76% (black): 1.75% 49+ VI: <20/40 Blind: ≤20/200 4% 0.7% 55+ VI: <20/40 Blind: ≤20/200 3.8% 0.75% 40+ VI: <20/40 Blind: (20/200 1.9% 0.3% 65+ VI: <20/40 (white):2.7% (black): 5.3%   Blind: ≤20/200 (white): 0.5% (black): 1.7%

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Visual Impairments: Determining Eligibility for Social Security Benefits (LaPlante & Carlson, 1996). Visual impairment was estimated as the “main cause of activity limitation” for 558,000 people of all ages in the United States in 1992, with “blindness in both eyes” accounting for 189,000 of these. Reported visual impairments were the main condition causing work limitation for 256,000 people ages 18 to 69, and were one of “all conditions” causing work limitations for 580,000 people in this age range. The employment and economic well-being of those reporting serious visual limitations is substantially affected, as the following section shows. Visual Limitations and the Workplace Unambiguous data on the prevalence of visual limitations among the population covered by the SSDI and SSI programs—working-age people ages 18-64, and children 0-17—do not exist. Nor do data on the employment and economic well-being of those populations. Quite detailed objectively reported data on the visual limitations of subpopulations in the United States and other countries are available based on professional evaluations by clinicians, as reviewed above. But most of these studies have relatively small sample sizes and focus on older populations that contain a relatively large share of men and women age 65 and older who are not actively seeking employment, are not eligible for Social Security disability benefits, and are unlikely to be representative of the younger populations that these programs cover. We found no clinically based samples drawn from random samples of the children and the working-age populations eligible for SSI or SSDI benefits. We were able to find nationally representative data on children and the working-age population, but these data, while rich in socioeconomic information, based all of their information about visual limitations on self-reports. Also, the questions asked were quite extreme in their attempt to identify visual limitations—for example, “Are you blind in both eyes?” Finally, because “blind in both eyes” and other serious visual limitations are relatively rare, even in quite

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Visual Impairments: Determining Eligibility for Social Security Benefits large nationally representative samples, only a small number of people is actually identified, and hence it is difficult to obtain reliable estimates for subpopulations with these impairments—children, working-age population, men, women, etc. An analysis of such self-reported data shows that there is substantial heterogeneity in the working-age population with disabilities. A study commissioned by the committee and included in Appendix A offers an approximation of the prevalence of visual limitations in the working-age population in the United States (ages 25-61) as well as their employment and economic well-being (Houtenville, 2001). Houtenville uses a random one-sixth sample of the working-age population reporting visual impairments (and other severe impairments), as well as a sample of the entire working-age population of the National Health Interview Survey (NHIS). Respondents were first asked if they had a health-based work limitation, and only then were they asked about the kind of impairment that limited their work (this procedure is referred to here as the choice-based sample). Because visual impairments are relatively rare in the working-age population, Houtenville pooled cross-sectional data from the NHIS for the years 1983-1996. For the one-sixth random sample for all years, Houtenville found that 0.17 percent of working-age men and 0.17 percent of working-age women reported being “blind in both eyes.” A larger percentage of men (4.89) and women (2.38) in this age range reported “some visual impairment.” For the sample of working-age men and women who are asked about their impairments only if they first report that they have a work limitation, the percentage of men (0.10) and women (0.08) reporting being blind in both eyes fell dramatically. The same situation was found for men (0.67) and women (0.39) reporting some visual impairment. Houtenville shows that choice-based samples that ask only those who first report a work limitation about their impairment reported a significantly lower prevalence of these impairments in the working-age population. Nevertheless, his prevalence findings using the one-sixth random sample are still somewhat lower than those found in the population-based studies reported in Table 1-1. This is of course in large part likely to be caused by the much younger average working-age population he considered.

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Visual Impairments: Determining Eligibility for Social Security Benefits Retrolental fibroplasia3 with macular scarring or neovascularization; or Bilateral congenital cataracts with visualization of the retinal red reflex only or when associated with other ocular pathology. The visual field listing criteria are the same for children as for adults. As noted above, a child’s impairments are considered to be functionally equivalent to the intent of the listings if he or she has “marked” limitations in two broad domains of function—cognition/ communication, social functioning, personal/behavioral functioning, and task completion—or an “extreme” limitation in one domain. THE COMMITTEE’S APPROACH The conceptual model underlying disability determination has been undergoing changes over the past several years, especially since the passage of the Americans with Disabilities Act (ADA) in 1990. The newer conceptualization follows a social model of disability, which postulates that factors both within the individual and in his or her physical and social/cultural environment combine to influence performance and participation in everyday life situations. This model replaces the earlier stress on disability or handicap, and the negative aspects of an individual’s situation, emphasizing instead the person’s remaining capabilities and how they can best be supported to permit full economic and social participation. The ADA, based on the social model, represents a commitment in the United States to help individuals with disabilities to participate as fully as possible in the society and the economy. 3   This is now more commonly referred to as retinopathy of prematurity. The International Classification of Diseases, Ninth Revision (ICD-9) allows for the use of either term.

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Visual Impairments: Determining Eligibility for Social Security Benefits The social model also underlies the approach now taken by the World Health Organization toward disability and handicap. Whereas the International Classification of Impairment, Disability, and Handicap (ICIDH) (World Health Organization, 1980) established definitions for these terms, the new International Classification of Functioning, Disability and Health (ICF) (World Health Organization, 2001) is an attempt to fully account for the interactions between the individual and the physical and social environment in determining the participation of an individual with a disability. Generic Concepts and Terms as Applied to Vision The committee carefully considered the social model as it applies to those with visual impairment, recognizing that a diagnosis of a visual disorder (or even the measured severity of visual impairment) does not inevitably predict a person’s disability or handicap. However, this model does pose a dilemma for using the measurement of impairment as a surrogate for determining level of disability. In reviewing data on visual testing and functional status, the committee’s paradigm was deceptively simple: visual loss, by some measure, is associated with increasing inability to carry out activities associated with employment or, in the case of children, age-appropriate activities. The data bearing on this issue present a more complicated picture, because the same level of visual loss can result in a wide spectrum of disability level, depending on such diverse factors as education, age, presence of other comorbid conditions, and social and environmental support. Thus, there is substantial variation in functional status for any given level of visual loss. The committee also carefully evaluated the fourth and fifth editions of the American Medical Association’s (AMA) Guides to the Evaluation of Permanent Impairment: Vision (American Medical Association, 1993, 2001). These guides are used in many workers’ compensation disability determination procedures and represent a more traditional quantitative approach to evaluating the disability resulting from specific levels of impairment.

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Visual Impairments: Determining Eligibility for Social Security Benefits The committee has chosen a framework that recognizes a continuum from disorder to handicap: as one progresses from disease or disorder to impairment, and then to disability and to handicap, many variables within the individual and in his or her environment interact to determine the level of function. Figure 1-4, adapted from a document prepared as background for the 2001 AMA guides (International Society for Low Vision Research and Rehabilitation, 1999) illustrates this continuum. Instead of the term “functional vision,” we use “visual task performance,” which in our view more clearly expresses the intended meaning: performance of real-world tasks using vision. At the left of the box are features of the organ (or organ system) and its function. Diseases, disorders, injuries, or other structural or physiological changes in an organ or organ system often lead to the outcomes we call disabilities, but they do not directly or unconditionally cause disabilities. Diseases or disorders affect the functioning of the organ system; in the case of the visual system, these are visual functions. Visual functions are measured using quantitative clinical tests, such as tests of acuity, visual fields, or contrast sensitivity. When we speak of visual functions we are referring to the performance of the visual system, more or less in isolation, under standardized measurement conditions. An organ system function that fails to meet some agreed-on criterion of normal status is said to be impaired. Impairment refers to a measurable deficit in what the organ system is able to do, compared with its normal function. It may be expressed in such terms as “systolic blood pressure of 180 mmHg” or “visual acuity of less than 20/60 on a Snellen chart.”4 The right side of Figure 1-4 describes the capabilities and performance of the whole person in the environment. It starts with skills and abilities, meaningful things the person can do, like reading, driving, 4   The ICIDH (World Health Organization, 1980) definition: “In the context of health experience, an impairment is any loss or abnormality of psychological, physiological, or anatomical structure or function” (p. 27).

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Visual Impairments: Determining Eligibility for Social Security Benefits   The Organ The Person Aspects: Structural change, anatomical change Functional change at the organ level Skills, abilities of the individual Social, economic consequences Neutral Terms: Health condition Organ function Skills, abilities Social participation Loss, limitation: Disorder, injury Impairment Disability Handicap ICIDH—80: Disorder Impairment Disability Handicap ICF: Structural change Functional change, impairment Activity + performance code Participation + performance code Application to Vision:   Visual functions --Measured quantitatively, e.g, visual acuity Functional vision * --Described qualitatively,e.g., reading ability   *Visual task performance in our framework FIGURE 1-4. Aspects of vision loss. Source: Adapted from International Society for Low Vision Research and Rehabilitation (1999).

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Visual Impairments: Determining Eligibility for Social Security Benefits keyboarding, crossing the street, or identifying birds. Generally, abilities are described more qualitatively than the raw visual functions, although this report examines some quantitative measures of visual task performance that might be considered by SSA. From the concept of ability, it is a short step to the concept of disability, a reduction in or loss of an ability. Examples of visual disabilities include difficulty reading normal size print and using tools or small machinery. As noted above, disability is recognized as a complex interplay between the individual, the complexity of the task, and the surrounding environmental and social supports.5 The term handicap, in modern practice, refers to the result of an interaction between a person and the environment. We use it only to refer to the negative result of the interaction between a person’s impaired abilities and the environment in which she or he is attempting to function. Thus a disability that prevents a person from climbing stairs imposes a handicap when that person must live, work, or otherwise participate or obtain services in a structure that has stairs and lacks wheelchair ramps, elevators, or other assistive devices. Although the disability may be real and permanent, it need not result in a handicap if the person has a suitably designed supportive environment in which to live and work or is able to use assistive technology.6 SSA uses “disability” or “disabled” as a term that applies to those who are deemed eligible for disability benefits as a result of the formal determination process. The agency uses the terms to describe the relationship of the person to the criteria for its programs, not 5   The ICIDH (World Health Organization, 1980) definition: “In the context of health experience, a disability is any restriction or lack (resulting from an impairment) of ability to perform an activity in the manner or within the range considered normal for a human being” (p. 28). 6   The ICIDH (World Health Organization, 1980) definition: “In the context of health experience, a handicap is a disadvantage for a given individual, resulting from an impairment or a disability, that limits or prevents the fulfillment of a role that is normal (depending on age, sex, and social and cultural factors) for that individual” (p. 29).

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Visual Impairments: Determining Eligibility for Social Security Benefits necessarily as a description of his or her personal functional status. The SSA disability determination process (already described) follows a path starting with a medical model, embodied in the listings of impairments, through Step 3 of the decision process; it then proceeds to a model that implicitly accounts for some social and physical environmental factors in the later steps, in which vocational factors are considered. The listed medical conditions are assumed to produce impairments so severe that individuals are disabled by the mere presence of the condition, as determined by physical diagnostic markers. For persons whose conditions meet or equal the listings and who are not engaged in substantial gainful activity, SSA does not require that functional capacity be evaluated to determine eligibility for benefits. For those whose conditions do not meet or equal the medical listings, SSA switches to an evaluation of functional capacity in relation to the work environment (based on a simplistic model of work). The process evaluates the claimant’s ability first to perform recent relevant employment and then to perform any work in the U.S. economy. The vocational grids mentioned earlier are used as decision aids when the impairment is in the ability to perform physical labor, but for other work, the guidance is sparse at best. The decision maker considers the claimant’s age, education, and work experience, and, by implication, transferable skills. At this time, SSA prescribes no formal tests or evaluation protocols to determine what the claimant actually can do, no formal method for determining what disability might result from an individual’s impairments in the living and work environments, nor what the mitigating effects of environmental accommodations or assistive technology might be. Vision-Specific Concepts and Terms As explained above, visual functions are measured using quantitative clinical tests. When we speak of visual functions we are referring to the performance of the visual system, more or less in isolation, under standardized measurement conditions. The specific visual functions considered in this study are:

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Visual Impairments: Determining Eligibility for Social Security Benefits visual acuity, visual fields, contrast sensitivity, color vision, binocular function, visual search. The committee also examined environmental conditions that may exacerbate visual impairments, chiefly extremes of lighting (glare, high or low luminance) and transitions between high and low luminance conditions. Full definitions of these visual functions are given in Chapter 2, which treats each of them in detail. The committee selected four task or activity domains as exemplars of everyday and work functions in which vision is an important contributor to performance capability. The committee sought to identify categories of tasks that are important across a wide range of daily life and work situations, that may be reasonable surrogates for visually intensive job tasks, that are of moderate complexity, and for which data are available in the research literature. The selection process is discussed in more detail in Chapter 3. After considerable discussion of candidate task domains, the committee chose the following: Reading and other sustained near tasks (e.g., computer use); Mobility, including both ambulatory and driving situations; Social participation, including visual communication; Tool use and manipulation, including hand-eye coordination. These domains were used as organizing concepts in our examination of the scientific evidence on relationships between visual functions and visual task performance.

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Visual Impairments: Determining Eligibility for Social Security Benefits Lines of Inquiry For the purposes of the SSA benefit programs, disability is defined by “the inability to engage in any substantial gainful activity, by reason of any medically determinable physical or mental impairment(s)” (Social Security Administration, 2001). SSA is required to document the disability of each claimant in the process of deciding whether he or she is eligible for disability benefits. Because disability represents the outcome of interactions between the person and his or her environment (both physical and social), there are many possible avenues for determining whether any individual claimant has a disability. The first and most obvious variable is the measurement of the physical (in this case, visual) impairment. The committee examined how this is now done by SSA and also examined evidence on best practices for current tests and on new or emerging ways to test visual functions. We established psychometric and other criteria that vision tests should meet if they are to be recommended for use in SSA disability determination. We also gave careful consideration to what visual functions should be measured, evaluating evidence both for the importance of the functions for task performance and for the availability of tests that met our criteria. Finally, the committee reviewed ways in which to combine test results into a composite index of visual impairment. Because disability occurs at the interface of visual ability and task demands, the next obvious area of inquiry was the determination of whether disability from visual causes could be determined by judging performance on a set of standardized tasks. In order to approach this issue, the committee selected a set of tasks or activity domains that represent common, visually intensive, job tasks. The committee pursued research on available survey-based job task taxonomies and datasets that include information on the visual requirements of jobs or job categories, which may serve to inform SSA policies or practices. The committee considered the utility of directly measuring performance on these surrogate tasks, seeking information on instruments available for this purpose. Other information sources were questionnaire instruments that gather self-reports of

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Visual Impairments: Determining Eligibility for Social Security Benefits performance abilities from individuals, notably health-related quality of life instruments. Such instruments that have been developed specifically for people with visual disorders have been used to demonstrate a relationship between visual impairment and task performance limitations, and we examined these carefully. The committee’s final line of inquiry was the examination of data on the employment and economic consequences of visual impairment. We commissioned studies of datasets generated by the National Health Interview Survey and the National Health and Nutrition Evaluation Survey, both nationally representative surveys conducted by the federal government that include information on self-reported disabilities and economic and employment status. Information Sources and Standards The committee and staff conducted literature searches in the peer-reviewed and technical literature (e.g., government-sponsored reports) on vision-related topics, testing, disability determination, disability programs, and other topics. For vision and vision testing, the peer-reviewed research and clinical literature was the predominant source, although many other sources were also tapped. Standards for Evidence Peer-reviewed scientific literature was the most desirable source of information for this study, and when it was available it was used. Committee members applied their professional judgment in evaluating the methodology of studies they reviewed, rejecting studies that appeared to be poorly designed, executed, or analyzed. Technical reports and other information sources, such as analyses of survey datasets, were evaluated for acceptability, with special attention to the data sources used in preparing the reports and to the methodology used. The committee often discussed the strengths and weaknesses of particular evidence in its deliberations.

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Visual Impairments: Determining Eligibility for Social Security Benefits When weaknesses were found but a report or study was deemed worthy of inclusion, the weaknesses are discussed along with the evidence in this report. The committee is especially careful to note the limitations of epidemiological and survey-based studies that could be used to infer characteristics of populations. Often the findings are worth discussing, but only limited inferences can be drawn because of the size or other characteristics of the study sample. In some cases, the committee commissioned specialists to perform data analyses, to ensure that the analyses were done by people who knew well the idiosyncrasies and limitations of the source data. Public Forum In the committee’s view, it was important to obtain input for this study from organizations providing services to people with visual impairments and advocating for their interests. The committee therefore organized a public forum to gather input from these communities. Representatives of national and regional organizations and others were invited to make presentations. A list of organizations invited to nominate speakers and a list of speakers and major topics appear in Appendix B. ORGANIZATION OF THE REPORT Three chapters follow this introduction. Chapter 2 lays out the committee’s findings on tests of visual function. Each function is examined in detail, and tests of the function are evaluated for their potential value in disability determination, with detailed rationale for the conclusions that we reached and the recommendations we made. Chapter 3 presents our findings on the relationships between visual functions and the tasks of everyday life. It discusses the four task domains found to be important, as well as evaluations of health-related quality of life studies and occupational analysis methods and datasets. Chapter 4 covers the special issues that affect how children’s visual function can and should be tested.

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Visual Impairments: Determining Eligibility for Social Security Benefits Each of these chapters includes recommendations for SSA actions on visual disability determination, as well as for research that will improve visual disability determination. The recommendations cover what aspects of vision should be tested, how the tests should be conducted, and how to combine results of tests if warranted. Suggestions are provided for future research to address issues that remain unresolved. Appendixes A through D provide the full text of one commissioned paper, the details of the public forum, a glossary of SSA terms, and brief biographical sketches of the committee members.