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Report of the Visual Impairment and Its Rehabilitation Panel

Visual impairment can be defined as any chronic visual deficit that impairs everyday function and is not correctable by ordinary spectacles or contact lenses. Although there have been important strides in the treatment and prevention of eye disease over the past few decades, there still exist many causes of vision loss for which there is no cure. Even with the best medical treatment, many Americans must live with impaired vision. The term visual impairment is used broadly in this report, covering a wide range of uncorrectable visual disorders including low vision and total blindness. A commonly used definition of low vision, advocated by the World Health Organization, is visual acuity worse than 20/60 with best refractive correction and/or significant visual field loss. In modern society, with its emphasis on reading and driving, some researchers use acuity worse than 20/40 for classifying low vision. "Legal blindness" represents an artificial distinction and has little value for rehabilitation, but it is significant in that it determines eligibility for certain disability benefits from the Federal Government. In the United States, it is typically defined as visual acuity with best correction in the better eye worse than or equal to 20/200 or a visual field extent of less than 20 degrees in diameter. These overly simple criteria for visual impairment are far from comprehensive in defining the visual function deficits that can cause difficulties with daily living tasks. Many other types of visual impairment are also of concern here because they hamper the performance of everyday activities—problems such as eye movement disorders, visual agnosias, visual processing deficits associated with old age, visual aspects of learning disabilities, and visual disorders of infants and children.

Estimates of the number of Americans with visual impairment depend on how it is defined. Some estimates indicate that there are more than 3 million Americans with low vision, almost 1 million who are "legally blind," and roughly 200,000 who are more severely impaired. Because of their reliance on narrow definitions of visual impairment, these figures underestimate the prevalence of visual impairment. When more broadly defined as visual problems that hamper the performance and enjoyment of everyday activities, other recent estimates indicate that almost 14 million Americans suffer from visual impairment. In adults, visual impairment is associated with loss of personal independence and difficulty maintaining employment, often leading to the need for disability pensions, vocational and social services, and nursing home or assistive living placement. Older adults represent the vast majority of the visually impaired population. Visual impairment is included in the 10 most prevalent causes of disability in America. For older adults, visual problems have a negative impact on quality of life, equivalent to that of life-threatening conditions such as heart disease and cancer. In children, visual impairment is associated with developmental delays and the need for special educational, vocational, and social services, often beyond childhood into adulthood.

The leading causes of visual impairment are diseases that are common in the elderly: age-related macular degeneration (AMD), cataract, glaucoma, diabetic retinopathy, and optic nerve atrophy. Over two-thirds of those with visual impairment are over age 65. Although there are no gender differences in the prevalence of vision problems in older adults, there are more visually impaired women than men because, on average, women live longer than men. However, blacks are twice as likely to be visually impaired than are whites of comparable socioeconomic status. It is estimated that there will be almost 34 million Americans over the age of 65 in 1999, and by the year 2030 this number will more than double. It is important to emphasize that as the older adult population grows, the number of people with visual impairment and other aging-related disabilities will increase.

The leading causes of visual impairment among infants and children are retinopathy of prematurity (ROP), cortical visual impairment, and structural ocular abnormalities, such as cataract and coloboma. These conditions occur during infancy and early childhood, when it is difficult to assess their effects on vision and quality of life. In addition, many of these conditions occur with increased prevalence in children with neurodevelopmental delay, further complicating the assessment of level of vision and the evaluation of quality of life. More boys than girls are visually impaired. Additionally, increasing numbers of infants are born very prematurely and survive. These children are at high risk for multiple disabilities, including visual deficits, and will substantially increase the number of Americans with visual impairment.

Program Description.The congressional legislation that created the National Eye Institute (NEI) mandates research on amelioration of the impact of impaired vision and blindness on health and well- being. The current NEI research program on visual impairment and its rehabilitation can be divided into six areas. Laboratory research is a fundamental yet often underappreciated pillar of research on visual impairment and blindness. A major goal of this area is to develop a scientific basis for understanding normal visual functioning that can be extended to explain the disabilities experienced by people with low vision, blindness, and other visual processing deficits. Examples include the role of vision in spatial cognition, factors that underlie text legibility and reading performance, and the role of visual attention in impaired vision. Ultimately, such a theory should explain how visual deficits affect performance of everyday activities and how to optimize the visual environment to enhance performance, especially in those with visual impairment. It could guide the development of appropriate rehabilitation strategies, adaptive technology, and assessment tools and indicate when it is more effective to convey information by nonvisual means. A comprehensive understanding will not result from studies only at the sensory "front end" of the visual pathway.

While most forms of visual impairment result from diseases of the ocular media, retina, or optic nerve, the consequences for everyday life come from the interaction of reduced visual input with other brain systems, including those responsible for motor control and cognition. Nor will a full understanding come from a narrow disciplinary focus. It is likely that the necessary insights for ameliorating the effects of visual impairment will emerge from interdisciplinary studies combining traditional approaches to vision research with methods from research on cognitive science, motor control, development and aging, psychology, neurology, computational modeling, and broader perspectives from neuroscience.

Another primary research area in visual impairment and rehabilitation is visual assessment and everyday task performance. Because vision plays an important role in most everyday activities, people with visual problems are routinely faced with significant challenges in their daily lives, such as recognizing objects and people, getting around (mobility), reading, socializing, working, and taking care of their daily needs (e.g., preparing meals and managing finances). Difficulties with daily activities can lead to conditions that seriously reduce quality of life, including depression, social isolation, educational problems, and employment challenges. All of these underscore the critical importance of research designed to minimize these difficulties among the visually impaired. There is considerable variability among visually impaired persons in their ability to perform everyday tasks, depending on their eye condition, its severity, duration and age of onset, task lighting conditions, as well as compensatory strategies and the existence of other medical problems and disabilities. The challenge for the clinician is to identify which tasks are problematic for a given patient so that a rehabilitation plan can be developed and implemented. Research on valid and reliable assessment tools that allow clinicians to properly identify and treat problems in performing daily visual tasks is absolutely essential to improving clinical care.

The logical partner of visual assessment is the rehabilitation process. Rehabilitation of the visually impaired individual, just as rehabilitation of the physically impaired individual, is directed at optimizing functional capabilities and quality of life. Rehabilitation is a multifaceted process involving the assessment of visual capabilities and the evaluation of functional performance (e.g., reading, writing, and mobility) within the context of lifestyle (e.g., employment, family activities), attitudes, and psychological well-being. Rehabilitation goals are defined in terms of what matters most in a person's life, and attempts are made to solve functional problems through adaptive options (e.g., vision enhancement and substitution devices, environmental modifications) and coping strategies. The research challenges are to: develop rehabilitation mechanisms that will be effective in enhancing quality of life, determine which approaches are most successful with different types of individuals, and improve the delivery of these services to those in need.

The area of technology and assistive devices is a critically important research area because of its central role in the rehabilitation process. This research focus includes: the development of new devices; application of advanced technologies to visual or sensory substitution aids; and the continuous development and exploitation of new technologies, including communication, information, and computer technology. In addition to developing assistive devices, it is essential that research in this area address how to optimize training in the effective use of devices. This includes a special emphasis on training the elderly, who comprise a substantial portion of the visually impaired population. Other issues central to research in this area are cost, accessibility, cosmesis, personal acceptance of visual rehabilitation devices, and ease of use.

Research on environmental access and modifications addresses the effects of visual impairment on accessing the surroundings in the home, in the workplace, and while traveling, and explores environmental modification strategies for increasing independence of visually impaired persons. Loss of independence, which includes mobility throughout one's own environment, seriously degrades quality of life in far-reaching ways, among them reducing access to social networks and to vision rehabilitation and other health services. Most vision rehabilitation strategies involve prescribing "personal" assistive devices (magnifiers and other optical devices) or providing training or other adaptations to visually impaired individuals. Environmental interventions, however, may serve to allow those with visual impairment to function better in the home, in the workplace, and in environments that are intended for public access, such as shopping malls, hospitals, and transportation facilities. Research on this topic seeks to identify the most effective environmental modifications and evaluate their ease of implementation, their level of acceptability, and their use by visually impaired persons.

Recent changes in healthcare financing have intensified public interest in the human costs of disability and the effectiveness of treatments and rehabilitation strategies for those affected. It is fully expected that strategies will have to be tailored to the special needs and goals of different subpopulations. To address these issues, research on visual impairment must include outcomes assessment. Outcomes include measures of self-perception of quality of life, assessments of the performance of everyday activities, employment status, independent living status, and educational attainment.

In Fiscal Year 1997, the NEI supported an estimated $3,800,000 in extramural research projects that emphasized on visual impairment and its rehabilitation.

The program goals for the area of visual impairment and its rehabilitation for the next 5 years are to:

• Improve our understanding of structure/ function in the visual central nervous system, neural plasticity, and the performance of everyday tasks, so that the visual processing capabilities of the visually impaired can be optimized.
• Develop assistive devices, environmental modifications, and rehabilitation strategies to minimize the impact of visual impairment in everyday life, and reduce disability and societal limitations among visually impaired persons.
• Determine which interventions are most effective and develop research tools so that these interventions can be scientifically evaluated, ultimately improving the clinical care of the visually impaired population.
• Establish the scope of impaired vision and blindness in our society and its ramifications for everyday life, identifying the prevalence of visual impairment and functional limitation and risk factors for visual disability, so that interventions can be targeted to high-risk subpopulations.

ASSESSMENT OF PROGRESS

During the past 5 years, there have been a number of accomplishments that span the six research focus areas discussed earlier.

Development and application of brain imaging methods to better understand neurological deficits and brain plasticity in visually impaired persons.Modern quantitative methods, including anatomical, electrophysiological, and brain imaging approaches (particularly functional magnetic resonance imaging [fMRI]) are telling researchers a great deal about the visual architecture of the brains of persons with neurological deficits. In addition, there is an increased understanding of the extent of plastic changes in the adult nervous system, which has implications for rehabilitative training and device development. There is some evidence that visual cortex is recruited for tactile functions for blind subjects. Work on brain plasticity over the past few years lays critical groundwork for addressing questions about neural plasticity in the visually impaired and how it may be exploited during the rehabilitation process.

Application of fundus perimetric methods for the evaluation of visual function in persons with central scotomas.Researchers have used the scanning laser ophthalmoscope (SLO) to assess visual function in patients with central visual impairment. Studies have demonstrated that patients with AMD tend to adopt fixation patterns that avoid placing scotomas below or to the left of fixation. This is interesting since placement of scotomas to the right of fixation slows reading more so than any other position. This fixation preference is different from eyes with macular holes or Stargardt's disease, a juvenile form of macular degeneration (MD), where patients tend to place the scotoma above fixation, and opposite to what would be expected based on reading studies in normally sighted readers. SLO testing has also shown that patients with central scotomas have much less stable fixation and different patterns of eye movements during tasks like visual search and reading than those without central scotomas.

A clearer understanding of the effects of visual impairment on everyday task performance.Research in the past 5 years has clearly indicated that understanding the effects of visual impairment on everyday task performance must include a consideration of cognitive, motor, and other sensory influences. In reading, visual recognition must be integrated with lexical, syntactic, and semantic knowledge. Clinical measures of acuity and contrast sensitivity are not by themselves good predictors of driver safety and performance, which also rely on visual attentional skills, a rapid speed of visual processing, and cognitive skills. Vision researchers have often tried to decouple visual function from cognition, motor behavior, and other sensory functions, but it has become clear that the role of vision in these tasks cannot be studied in isolation. Both a theoretical and a practical understanding of the complex visual tasks of everyday life will almost certainly require researchers to understand how visual information is integrated with multimodal information in a dynamic manner. Computational modeling approaches are feasible and useful in understanding the component mechanisms of visual behavior, as illustrated by the development of a computational model for reading.

A better understanding of how visual impairment impacts mobility.Recent research is beginning to clarify how visual impairment impacts mobility. For instance, visual impairment reduces walking speed, increases the number of collisions with objects and people in the environment, and increases perceived mobility difficulty, the cognitive demands of walking, and driving difficulty as well. In addition, visual impairment can lead to an increased risk of falling and fear of falling, an elevation in crash risk when driving, and, in general, reduced mobility and loss of independence. Some of these effects appear to be exacerbated under conditions of poor illumination or low contrast. Visual field extent, contrast sensitivity, and motion thresholds are associated with mobility performance, but conventional measures of visual acuity are typically not strong predictors. Knowing how visual impairment affects mobility is essential for developing effective rehabilitative regimens and assistive devices.

Development of rehabilitation strategies and programs for the visually impaired.There has been recent progress in the development and evaluation of rehabilitation programs for the visually impaired. A recent study found that visually impaired veterans report that they use and benefit from assistive devices that they were trained to use. A framework has been proposed that views low vision rehabilitation as a subspecialty of rehabilitation medicine, an established branch of health care that is sensitive to the multifaceted process of coping and compensating for disability. This broader perspective for vision rehabilitation may assist in integrating it into mainstream health care, facilitating appropriate reimbursement procedures, and ultimately providing more visually impaired persons with access to rehabilitation services. Proposed models of vision rehabilitation need to be evaluated to determine their effectiveness for various patient populations.

Development of improved optical and electronic reading devices.A number of new low-vision telescopes have been developed, with most emphasizing more acceptable appearance. Some offer new autofocus capabilities and flexibilities for in-office fitting and demonstration of the device. New stand magnifiers have been introduced that enhance ergonomics (comfort and ease of use), and the autofocus binocular low-vision telescope has been improved. With the rapid development of speech synthesis, more computerized systems using speech output are being developed for the visually impaired for use with desktop computers and portable handheld devices and for access to the Internet.

Improvements in text navigation and computer access.Research has explored the efficacy of several methods of presenting magnified text on computer screens, and these approaches have been incorporated into commercially available computer-based reading devices for low vision. These devices present text in a variety of formats (e.g., scrolled, rapid serial visual presentation, or spoken synthesized speech), which may be easier for visually impaired people to read and gain access to the World Wide Web, an increasingly important resource in society. Guidelines for making computers and computer-controlled devices accessible for a variety of disabilities, including vision, are available through the University of Wisconsin's Trace Center (http://www.trace.wisc.edu).

A common problem encountered by the visually impaired when reading magnified text (such as on a closed-caption television [CCTV]) is locating the beginning of the next line. Products have been developed that can assist the visually impaired in this challenge. These presentation modes can also be used with text already available in digital forms. In addition, there have been a number of optical and electronic devices employing new techniques and approaches. Over the past 5 years several new head-mounted electronic low-vision devices have been designed. Research on the utility of these devices is in the preliminary stages. This technology offers the opportunity to provide the high magnification of the CCTV in a portable format, and it may even be possible to provide a wider (virtual) field of view than is practical with a desktop monitor. These devices may offer new advantages in addition to magnification (such as enhancement or field compensation) that could present new visual opportunities. However, much more research and development is needed in this area.

Development of new technologies to enhance wayfinding capabilities of the visually impaired.A key advance identified as an important priority in the prior plan is the development of promising new technology to improve wayfinding in visually impaired persons. Remote signage systems have been developed and commercialized in which installed transmitters serve as signs that can be read and conveyed via electronic voice to users equipped with appropriate handheld receivers. Other developments include a talking map system for route planning that gives voice feedback in response to touch on a touch-sensitive screen, and a route planning database system that allows visually impaired travelers to plan travel routes from street maps stored on computer. Personal guidance systems have been developed that use computer-based maps and landmark information in combination with satellite-based global positioning systems for registering a traveler's present position. Some of these exciting new developments, while still in need of improvement and evaluation, are already available on a limited basis to consumers.

Progress in the evaluation of infants and children with or at risk for visual impairment.There has been recent progress in the ability of researchers to assess infants and young children who have or are at risk for low vision. The Teller Acuity Card procedure, which measures the finest grating that a child can resolve by observing the child's eye and head movement responses to black-and-white gratings (stripes) on a gray background, has been used to measure visual acuity annually in more than 1,000 infants in the NEI's multicenter Cryotherapy for Retinopathy of Prematurity Study. Because the Teller Acuity Card procedure does not require the participant to follow instructions or give a verbal response, it can also be used to test visual acuity in noncommunicative and cognitively impaired elders. Test-retest reliability and interobserver agreement are good, but the validity of the test in these patient groups has not been established.

Another assessment tool developed recently for use with infants and young children is the Low Vision Battery. This instrument assesses functional vision in infants and children whose vision is too low to be measured with the Teller Acuity Card procedure. To date, the Low Vision Battery has been used primarily in children with cicatricial ROP, but it has the potential to provide useful information on functional vision in infants and children whose low vision is caused by other problems.

Increase in the use of epidemiological and survey research methods to understand the scope and impact of visual impairment and disability.Epidemiological and survey research on visual impairment is beginning to indicate that the scope of functional impairment and disability from eye conditions is much more prevalent than previously thought. Certain subpopulations in American society, such as the elderly, are more vulnerable than others, and the diversity of vision problems in terms of their impact on everyday life is broader than originally anticipated. This research, although in its infancy, serves as important groundwork for targeted investigations in this area and has direct implications for healthcare planning and public health projections. There has also been progress toward development of a vision-targeted, health-related, quality-of-life questionnaire that is applicable to the special circumstances of the visually impaired population. These instruments assess the impact of visual impairment in daily life from the individual's own perspective and address a number of important domains, such as difficulty in daily tasks, coping, and general health and functioning. These instruments are essential for evaluating rehabilitation strategies and understanding the reasons for success or failure of the rehabilitation process.

PROGRAM OBJECTIVES

Program objectives for the next 5 years in the area of visual impairment and its rehabilitation include both basic and applied research.

• Develop a theoretical understanding of normal visual functioning that can be extended to understanding and treating the disabilities experienced by people with low vision.
• Understand the visual requirements of everyday tasks.
• Develop effective assistive devices and techniques to maximize residual vision and/or substitute for visual information.
• Develop environmental designs and modifications that enhance independence among the visually impaired.
• Evaluate the effectiveness of rehabilitation in the visually impaired.
• Ascertain the prevalence and incidence of visual impairment and visual disability in the United States and identify subpopulations at heightened risk for visual impairment and disability.
• Create an effective infrastructure for research on visual impairment and rehabilitation.

The needs and opportunities related to each of these objectives and the strategies for accomplishing them will now be considered.

Objective 1: Develop a theoretical understanding of normal visual functioning that can be extended to understanding and treating the disabilities experienced by people with low vision.

Research Needs and Opportunities

Laboratory and clinical research are important components of the NEI's research program on visual impairment because they provide the knowledge base for improving and enhancing the perceptual processing capabilities of the visually impaired and for designing sensory substitution methods for the profoundly impaired or totally blind person. It is difficult to generalize a theoretical principle to low vision and blindness if it is still poorly understood for normal vision; therefore, the study of the normally sighted does have an important role in the study of visual impairment and its rehabilitation. Research is needed on the visual mechanisms underlying object recognition, mobility, skilled movement, and reading. Many currently popular topics in basic vision research are ripe for addressing issues relevant to visual impairment and its rehabilitation, especially for those with low vision.

Strategic Research Questions

What areas of basic vision research need to be emphasized to improve and enhance the perceptual capabilities of the visually impaired?

Depth Perception and Binocular Processes—It is unclear to what extent those with low vision can benefit from stereo, which is a powerful and routine depth cue for the normally sighted. Anecdotal reports suggest that some persons with low vision make veridical depth judgments under certain circumstances. Additional research is needed to determine the basis for these judgments and how this process could be facilitated in those who have deficient depth perception skills. The relative motion of objects at different distances also provides powerful depth information for people with normal vision. Research has shown that key aspects of motion perception are resistant to blur and contrast reduction, and may therefore be important cues to depth for visually impaired persons. Persons with MD (especially prevalent in the elderly) often read better with one eye covered, yet the reasons for this are not well understood. The conditions under which those with bilateral macular disease achieve binocular fixation need to be determined.

Multimodal Sensory Integration—There is a need for a more fundamental understanding of multimodal sensory integration in constructing perceptual representation of objects in space. This could be especially helpful for the design of high-tech assistive technology that is designed to provide information through more than one modality. For example, is there a principled way of combining visual and acoustic information to provide access to graphical-user interfaces (GUIs) for people with visual impairment? Similar considerations apply to mobility aids that demand integration of visual, acoustic, or tactile information.

Computational Modeling—Over the past decade there have been many strides in the development of computational models for normal visual processes, such as shape recognition and object recognition. Recent work with computational models of eye movement control during reading have demonstrated the utility of this approach to problems of particular relevance to the understanding of impaired vision. Computational modeling could be useful in understanding the mechanisms underlying visual task performance and visual behavior by incorporating the interaction of vision with motor, cognitive, and other sensory systems. The consequences of visual impairment in task performance could be assessed in terms of its impact in the model's output. Compensations in other aspects of the model could be considered that may offset the effects of impaired vision. In this way, computational models could not only assist in understanding the breakdown in a visual process but also may also suggest rehabilitation approaches.

Field Loss—Researchers need a better theoretical understanding of the information processing characteristics across the full visual field, how these characteristics are perturbed by eye disease, and how the processing capabilities of the remaining visual field, including the visual attention system, can compensate in performing visual tasks. A key unresolved issue is the question of functional equivalence of central and peripheral vision following size scaling (M-scaling). Many simple visual tasks (e.g., target detection) can be performed equally as well in the periphery if targets are suitably increased in size to compensate for differences in spatial resolution. But there is good evidence that for more complex visual tasks (e.g., reading), central and peripheral vision cannot be made equivalent by size, implying other critical processing differences in central versus peripheral field.

Most of the prior work on field loss has focused on central scotomas, given the high prevalence of AMD among older adults. It is technically difficult to place images at known retinal locations of people with central loss and map their visual fields accurately and reliably. The SLO has played an important role in this area, including the development of macular perimetry techniques that control for eccentric fixation or changes in the direction of gaze. However, there is also a need for simpler techniques that are more widely available.

Peripheral field loss is an often-neglected area of research, despite its importance in a variety of daily tasks such as mobility, driving, and searching for and locating objects of interest. Glaucoma, stroke, and retinal degenerations that cause peripheral vision problems are relatively prevalent in society, and individuals with impaired peripheral fields need rehabilitation options.

Neural Plasticity—Efforts to understand neural plasticity must continue, especially in terms of how the central nervous system is reorganized after visual processing is disrupted or drastically impaired through disease or injury. It is possible that this plasticity could be exploited to enhance the use of residual vision or other sensory and cognitive systems in visually impaired persons. Little is known about whether there are plastic changes in the visual cortex of people with congenital forms of low vision or for those with late-life-onset low vision, such as the elderly. For example, do changes occur in the visual cortex of people suffering from MD? Do training programs that encourage the use of peripheral vision for traditionally central vision tasks (e.g., reading, object recognition) result in changes in the underlying cortical representation? Understanding brain plasticity may also help to explain difficulties encountered by older adults in learning to read by touch (Braille). Answers to these questions are important for understanding long-term adaptation to vision loss, for designing training programs for using peripheral vision and sensory substitution methods, and in evaluating the potential success of therapies for retinal degenerations.

Objective 2: Understand the visual requirements of everyday tasks.

Research Needs and Opportunities

Difficulties with daily activities can lead to serious reductions in quality of life, including depression, social isolation, educational problems, and employment challenges. A better understanding of the role of vision in everyday task performance is critical for designing effective rehabilitation programs. Given the stimulus and environmental complexity of everyday activities and the multiplicity of skills and modalities a person brings to bear on the situation, the study of task performance is not easy. Nevertheless, efforts to develop measurement strategies are not insurmountable as illustrated by recently developed methods for measuring reading skills in those with low vision. Similar efforts need to be extended to a wider variety of daily activities and toward developing a better understanding of why two individuals with similar eye conditions and impairment levels can exhibit very different task performance capabilities.

Strategic Research Questions

What aspects of visual function need to be better understood to determine the requirements of the visually impaired to carry out everyday tasks?

Multidisciplinary Assessment—Visual acuity is the traditional gold standard for visual function evaluation in the clinic, but previous research has indicated that other aspects of visual function are also useful in characterizing problems in visual task performance. For example, contrast is important in predicting mobility skills, and visual processing capabilities across the visual field are important in driving performance. There is widespread sentiment that the search for a battery of visual sensory tests may be an overly simplistic approach to understanding the mechanisms of visual performance deficits among those with low vision. A problem with much of the previous research on task performance is the almost exclusive emphasis on visual predictors in isolation. Future research should focus on the cognitive, motor, and multisensory components of these tasks and examine how visual performance limitations are affected by coexisting deficits in these domains. Older adults and premature infants may be two such groups who could substantially benefit from this multimodal approach, since they often have cognitive, physical, and/or hearing impairments in addition to their vision loss. Continuing this multidisciplinary theme, there is also a need for research on basic psychosocial processes and dynamics that addresses the motivational factors underlying rehabilitation and the desire for personal independence.

Higher Order Visual Processing—Most previous research has focused on three visual sensory functions—acuity, contrast sensitivity, and visual field sensitivity—and has neglected to closely examine higher order visual processing skills. In preliminary studies, visual processing speed, visual search and attention, motion perception, eye movements, and fundamental components of object recognition appear to have promise in understanding performance problems. The issues need to be addressed as mechanisms underlying visual difficulties in those with low vision.

Visual Requirements for Complex Tasks—Other performance measures in need of development are an orientation and mobility course with standard components, as well as the refinement of definitions of "adverse" mobility measures such as falling, tripping, vehicle crashes, and injuries, which can occur during mobility.

Examples of other common visual tasks that deserve consideration as performance measures include: simulated common settings in which visual tasks can be quantitatively assessed, telephone use, locating objects in cluttered areas, face recognition, filling out a form such as check writing, and use of GUIs on computers and other electronic displays. Researchers embarking in this field may find some guidance from the field of gerontology, where performance-oriented tests have been successfully developed for assessing the instrumental activities of daily living in older adults. These tests are not always visually oriented, but they do demonstrate that complex skills can be analyzed into quantifiable behaviors.

Performance tests for visually impaired infants and children will obviously have to be geared to the specialized everyday activities of these age groups, but are also of high priority if the effects of early interventions on these developmentally challenged populations are to be properly studied.

Objective 3: Develop effective assistive devices and techniques to maximize residual vision and/or substitute for visual information.

Research Needs and Opportunities

There is a high priority for the development of effective assistive devices and techniques to maximize residual vision and/or substitute for visual information to enhance the performance of everyday tasks by the visually impaired. These devices take a variety of forms, including software technology and computer design, optical and electro-optical devices, light and glare control devices, and visual system transplantation techniques. The fundamental rationale underlying these devices is to enable visually impaired persons to function despite their impairment, to be more independent and productive, and to be able to fully participate and enjoy all aspects of society. Special efforts should be directed toward developing rehabilitation options for visual problems for which there is little help available. Some of these areas include small field-of-view telescopes, devices for intermediate-distance tasks, peripheral field expansion, computer-assisted technology heavily based on icons, and coping with and adapting to the use of assistive devices.

Strategic Research Questions

What needs to be considered in the development of assistive devices and related techniques to maximize residual vision?

Many high-priority questions remain with respect to device development. The technology underlying magnifiers is mature, but more ergonomically successful ways to use them must be identified. Can a wide-field telescope be designed and marketed? Are there effective methods for field enhancement? The population least served by low-vision services are persons with restricted visual fields, including both "tunnel vision" and hemianopsia due to glaucoma, retinitis pigmentosa, or stroke. The existing devices for increased field awareness have not proven to be effective on a widespread basis. The problem with most approaches can be traced back to the inadequate model of visual function throughout the peripheral field, and especially for those with field losses. Effective solutions to this problem must go beyond the static concept of the reduced visual field, which neglects the scanning function of eye movements and misrepresents the actual everyday situation. There is a need to better characterize and understand dynamic visual function in patients with field loss, so that effective devices can be developed.

There is a pressing need to deliver help to the hundreds of thousands of persons who are visually impaired. Researchers should not neglect device development that relies on techniques and methods that can be realistically applied and implemented in existing rehabilitation services. There has been a great deal of emphasis on developing devices that are "low cost," and this is a laudable goal. However, high cost should not be a deterrent to researchers and engineers if the device shows great promise in solving a significant problem for the visually impaired.

Computer GUIs that are highly visual present a problem for visually impaired persons who need access to computers. The increased use of computer GUIs in many aspects of life (automated tellers, shopping, telephones) and the clear potential for growth in this area require the development of ways of presenting key information in alternative or enhanced formats so that the visually impaired still have access to it. In general, GUI formats are not optimally designed, even for those with normal vision, and therefore provide little guidance for design adaptations for those with visual deficits. Further research in this area will clearly help both normally sighted and visually impaired GUI users.

Objective 4: Develop environmental designs and modifications that enhance independence among the visually impaired.

Research Needs and Opportunities

Environmental modifications must be developed and evaluated to facilitate daily living, improve access to opportunities, and promote active participation by visually impaired persons in society.

Strategic Research Questions

What needs to be considered in the development of environmental designs and modifications to facilitate the daily living needs and independence of the visually impaired?

Tactile Perception—There needs to be a better understanding of the principles underlying tactile discriminability and symbol meaning for those who have never had visual experience and for those who lost vision late in life and are familiar with letter forms and other "visual" conventions. The tactile capabilities of older visually impaired people need to be evaluated, especially those who experience vision loss late in life. For example, are raised letters an effective communications medium to use in public areas such as signage and transaction machines? There has been some work on age-related deficits in tactile sensitivity, but such findings need to be evaluated in terms of their relevance to real-world tasks performance.

Travel—There must be improved understanding of the factors that reduce travel independence in visually impaired persons, especially older adults, when driving, walking, and using public transportation. Reduced mobility is associated with depression and social isolation; thus, improved mobility in the visually impaired is likely to enhance their general health and functioning and their enjoyment of life. Although there has been progress in developing wayfinding technologies, these wayfinding aids must be implemented on a broader basis and evaluated to determine if they are comprehensive enough to allow effective route planning and independent travel, and if visually impaired persons could be trained to use them effectively. Research on wayfinding strategies must not neglect the special needs of people who lose vision in late life, who may find it more difficult to learn to use technically challenging devices. Night driving is a significant problem for increasing numbers of older persons with age-related vision losses and for those with retinal degenerations regardless of age. Research is needed to address this problem both with devices and with environmental modifications that enhance visibility and reduce glare.

Lighting and Interior Design—Visual detection and identification of objects and events in the environment can theoretically be enhanced through improved lighting and interior design in the home and the workplace. Given the wide variability in visual capabilities and needs in visually impaired individuals, methods for evaluating needs and prescribing environmental interventions would be extremely useful, especially those that can be carried out by the visually impaired individual or by untrained family members, friends, or coworkers. Many persons with low vision have a greatly restricted range of luminances within which they can function effectively. Increased lighting may enhance visibility for some people with low vision, but it can result in glare that diminishes visibility for others. Specific methods are needed for assessing lighting requirements and simple ways of adjusting intensities and contrasts, along with effective ways of disseminating this information to lighting engineers, designers, and the public.

Technology—Existing digital technologies may be useful in developing devices to aid in managing everyday "visual" tasks. For example, barcode readers have been successfully developed as shopping aids, allowing price and product information to be presented to the visually impaired consumer in alternative formats. Wider application of this technology to assist visually impaired persons in coping with highly visual yet necessary activities of daily life should be explored and evaluated. Internet-based communication is quickly producing a new kind of environment in which social interaction and commerce can be conducted without travel. While some progress has been made, there still remains the need to develop and evaluate accessible World Wide Web browsers and software technology to ensure accessibility through alternative presentation, such as electronic magnification, voice, and refreshable tactile displays. This would allow visually impaired persons to take advantage of this increasingly important information source in society. Standard interfaces for interactive transaction machines (e.g., banking, vending, transportation ticket purchase) would go far in enhancing access by visually impaired persons.

Objective 5: Evaluate the effectiveness of rehabilitation in the visually impaired.

Research Needs and Opportunities

There is a growing consensus that strategies and procedures designed for the rehabilitation of visually impaired persons must be evaluated for effectiveness, either through multisite clinical trials or through smaller scale intervention evaluation studies. The emphasis on this type of research in future years stems from the realization that, until now, researchers have accumulated very little scientific data on effectiveness, i.e., "what works versus what doesn't." Several studies have reported benefits from rehabilitation programs and training protocols, but without rigorous design features like controls for bias and confounding, these studies are far from conclusive. Survey research on visually impaired patients' attitudes and beliefs about the usefulness of visual rehabilitation is informative, but it does not replace clinical trial research that would provide for a "fair test" of the hypothesis that the rehabilitation program under study is effective.

Strategic Research Questions

How do researchers determine if the strategies and procedures designed for rehabilitation of the visually impaired are effective?

Quality-of-Life Outcome Measures—This area has been hampered by a lack of measurement tools for important outcome variables. Reliable and valid outcome measures must be developed before a clinical trial on the effectiveness of rehabilitation programs can be properly evaluated. As discussed previously, there has been progress toward developing a vision-targeted, health-related, quality-of-life measure, but these types of measures are primarily targeted at patients with active disease processes rather than persons with untreatable visual impairment. These quality-of-life measures, such as the NEI-Visual Functioning Questionnaire (NEI-VFQ) must be evaluated with respect to persons whose visual impairment is uncorrectable and untreatable, and tailored so that they are responsive to issues related to rehabilitation and life with an impairment that is not likely to be cured in the future.

Measuring Task Performance—Although a person's attitudes and beliefs about their own health and well-being are critical outcome measures in clinical trials, there is also a need for outcome measures that reliably and validly assess the performance of the visual activities of daily living (e.g., reading, mobility, object search and recognition). These performance measures must be standardized and psychometrically sound. There has been some reluctance to develop performance task measures because not only vision but many other functional systems (e.g., physical capabilities, hearing, and cognition) impact the ability to carry out routine daily activities. However, the importance of these measures for determining the effectiveness of various rehabilitation services and approaches underscores the need for persistent research efforts in this area. Also, developing tools to measure visual rehabilitation "potential," analogous to the Functional Independence Measure widely used in physical rehabilitation, are also needed. This type of prognostic indicator could assist clinicians in more effectively promoting skill development and the use of compensatory strategies.

Assessment of Special Subpopulations—Special attention needs to be directed toward rehabilitation efforts for the aging population, since the prevalence and incidence of visual impairment is highest in this age group. The elderly often have coexisting impairments in hearing, cognition, and movement, which must be taken into account when developing effective rehabilitation strategies for this population. Intervention evaluation should utilize outcome measures that address visual performance as well as quality of life. The evaluation of rehabilitation efforts for visually impaired infants and children is also of high priority and should include an assessment of the role of visual stimulation. Because of the wide range of neurodevelopmental abilities of young children with low vision, studies that evaluate the effectiveness of intervention strategies will need to use assessment tools appropriate to both the visual and the developmental status of children to be studied. For adequate assessment of functional vision, there will need to be continued investigation of nonvisual acuity measures of functional vision in infants and children (e.g., the Low Vision Battery and white sphere kinetic perimetry). Another strategy would be to develop new assessment tools (e.g., a measure of contrast sensitivity for clinical testing of infants and children) and a quality-of-life assessment tool for infants and young children who have low vision.

Objective 6: Ascertain the prevalence and incidence of visual impairment and visual disability in the United States and identify subpopulations at heightened risk for visual impairment and disability.

Research Needs and Opportunities

A great deal of the early work on visual impairment and blindness was carried out with rather small samples, adopting an experimental research design tradition. However, to determine the scope and magnitude of visual impairment and disability in society, large-scale studies must be undertaken. There is a pressing and obvious need to study visual impairment and disability in the elderly, since they represent a large and growing segment of the visually impaired population.

Strategic Research Questions

What is the prevalence and incidence of visual impairment? Epidemiological research tools using larger samples may prove to be critical in addressing questions about the etiology of visual performance problems and quality-of-life reductions among the visually impaired, and for identifying important differences among various subpopulations of visually impaired persons (e.g., children, elderly, totally blind, low vision). The field of epidemiology emphasizes the scientific importance of case definitions for disease, impairment, and disability; the selection of controls; the assessment of bias and confounders; and multivariable statistical evaluation. All of these are critical issues in research on visual impairment and its rehabilitation.

Epidemiological research in this area serves two important public health functions—it generates information that can be used in population projections for healthcare needs in future years and it identifies potentially underserved populations: infants, children, the elderly, minorities, and the medically uninsured. Epidemiological research also allows for the development of risk factor models of visual disability—identifying the likely causes of visual disability and reduced quality of life among those with visual impairment; determining the diversity in the rehabilitation needs among the visually impaired; and understanding why some people adjust and cope while others are less successful and less likely to benefit from current rehabilitation practices. At a broader level, epidemiological research is geared at prevention of disease and disability in society, which is a fundamental goal of the National Institutes of Health (NIH). This is an area that needs more work with respect to visual impairment and eye disease.

Objective 7: Create an effective infrastructure for research on visual impairment and rehabilitation.

Research Needs and Opportunities

In previous national plans of the NEI, concerns were expressed about the slow progress of research on visual impairment. The reasons underlying slow progress in prior years are varied, but the thread that runs through all problems in this field is the lack of an effective infrastructure for research on visual impairment and rehabilitation.

Strategic Research Questions

What is the most effective strategy to ensure that these objectives are met? The single most effective strategy that could be implemented to ensure that all the above program objectives are met is to modify the current research infrastructure for funding research on visual impairment and its rehabilitation. A major impediment to attracting researchers to work on visual impairment and blindness has been that both clinical and laboratory vision researchers receive little or no training in research in visual impairment—its theoretical framework, methodology, or analysis. Ophthalmologists, optometrists, and special education and visual rehabilitation professionals understand the medical and visual needs and functional problems of their patients, but they rarely receive comprehensive training in research methods that supports high-quality research. A disproportionately large number of those doing research on visual impairment have been trained as experimental psychologists specializing in visual perception and psychophysics. But even among perception psychologists, impaired vision is usually considered a tangential topic. Furthermore, few psychologists have an opportunity to train in the clinical aspects of visual impairments, epidemiological research methods, and clinical trials, without which it may be difficult to formulate research programs that are both theoretically sound and clinically relevant. One way to address this problem would be to broaden the scope of funding mechanisms such as the clinician-scientist award (K08) to include those with training in special education, rehabilitation, or engineering, who wish to establish careers as independent scientists in the field of visual impairment and blindness. Conversely, a mechanism to provide laboratory research scientists (e.g., experimental psychologists and neuroscientists) with training in clinical aspects of visual impairment and rehabilitation and epidemiological and clinical trial methodology would provide a critical disciplinary basis for rigorous scientific work on visual impairment.

To attract vision scientists to the field of low vision, the NEI issued a request for applications in 1985. As a result, the number of grants addressing visual impairment and blindness increased from 6 in 1984 to 22 in 1988. With some fluctuation in this figure over the past 8 years, it remained at a similar level (19) in 1996. The majority of these are Small Business Innovative Research (SBIR) grants, with the percentage of R01 proposals addressing visual impairment and rehabilitation decreasing over the years. Peer review panels must be specially attuned to this area during the next 5 years if progress is to accelerate to an acceptable rate.

Research on visual impairment and blindness depends on the multidisciplinary contributions of vision scientists, clinicians, rehabilitation specialists, and engineers. Unfortunately, there are few opportunities for this type of close collaboration. A fundamental problem in this area is that the field is diverse and multidisciplinary, and interested parties do not know how to locate high-quality research expertise. Research organizations studying visual impairment and rehabilitation could go far in stimulating multidisciplinary efforts. Such groups should be encouraged to focus on both intervention development studies (i.e., laboratory research) and intervention evaluation studies (e.g., clinical trials), as well as providing core research support for investigators and information dissemination to the general public.

Research organizations specializing in visual impairment could also foster the much-needed interaction between vision researchers and the engineers and software developers who have been active in developing assistive technology to visually impaired persons, including that funded through the SBIR and the Small Business Technology Transfer Research programs. These groups could also provide support and access to patients for studies that extend beyond the limitations of traditional clinics. An ongoing problem in research on visual impairment is identifying visually impaired persons who may be interested in participating in research studies. Eye clinics usually deal with patients who are in an acute phase of an often-fluctuating eye disease, rather than patients with stable conditions who may be more amenable to research. Many of the patients seen in low-vision clinics are entrenched in psychosocial adjustments associated with coping with vision loss, making them less likely to be interested in research participation. A facility that is charged with organizing and recruiting visually impaired subjects into research protocols would serve a very valuable research function.

The next 5 years of research on visual impairment and blindness can lead to great strides in improving the quality of life for the visually disabled population in our society. These accomplishments can be realized if the existing research infrastructure is enhanced and there is a broad-based program to educate researchers, clinicians, and engineers from a variety of backgrounds about the availability of these resources.

VISUAL IMPAIRMENT AND ITS REHABILITATION PANEL

CHAIRPERSONS

Cynthia Owsley, Ph.D.
University of Alabama School of Medicine
Birmingham, AL

Gary S. Rubin, Ph.D.
Wilmer Ophthalmological Institute
Baltimore, MD

PANEL MEMBERS

Aries Arditi, Ph.D.
The Lighthouse Inc.
New York, NY

Velma Dobson, Ph.D.
University of Arizona
Tucson, AZ

Donald C. Fletcher, M.D.
Retina Consultants
Fort Myers, FL

Gordon Legge, Ph.D.
University of Minnesota
Minneapolis, MN

Eliezer Peli, O.D.
Schepens Eye Research Institute
Boston, MA

Joan Stelmack, O.D.
Hines VA Hospital
Hines, IL

NEI STAFF

Michael D. Oberdorfer, Ph.D.
National Eye Institute, NIH
Bethesda, MD