The American Occupational Therapy Association (AOTA)28 describes two national systems that exist to serve people with visual impairments—the blindness system and the health care system—noting that "delivery of low vision rehabilitation services through the health care system is not as well established as that of the blindness system." Goodrich30 suggests that access to vision rehabilitation services might have been greater had they been developed under a medical model. Service providers find it difficult to be compensated, and the visually impaired find it difficult to afford the devices and training they need.30
Vision rehabilitation shares certain general principles with other areas of rehabilitation, including:
However, compared with vision rehabilitation, general rehabilitation services more often involve medical or surgical therapy to address the underlying disease or injury. Such services are more likely to be delivered in the context of inpatient or hospital care and to be overseen by physicians or other medical professionals. As such, general rehabilitation services are represented predominantly in the upper rows of the framework for rehabilitation (Figure 1).
Vision rehabilitation services are rarely provided in an inpatient setting unless vision loss is secondary to another disability which necessitates an inpatient stay, such as head injury or stroke. Vision rehabilitation is focused instead on outpatient services delivered by providers outside of the health care system. This may be due to the fact that "[m]ost eye diseases...lack symptoms until vision is lost. Vision that is lost cannot be restored.... While important strides have been made in the prevention and treatment of eye disease, there is no cure for many causes of vision loss....While nothing medically can be done for patients with low vision, their quality of life can be greatly improved."4 (Surgical treatment for cataract does not require followup rehabilitative services, and therefore does not fall under the category of vision rehabilitation.)
Rehabilitation for vision impairment typically focuses on skills training (e.g., use of a long-cane) and environmental modification (e.g., improved lighting and contrast in the home) as well as psychosocial supports. Vision rehabilitation is more likely to be provided and funded outside of the health care delivery system, for example by charitable organizations or social services that address both medically and nonmedically defined needs. As such, vision rehabilitation services are represented predominantly in the lower two rows of the framework for rehabilitation. This is illustrated in Figure 3 (25 KB), which applies the framework to vision rehabilitation, using the example of AMD.
AMD is a partial breakdown of the insulating layer between the retina and the choroid (the layer of blood vessels behind the retina). Destruction of the retinal nerve occurs when fluid leaks into the choroid and forms scar tissue. These physiological changes may lead to impaired vision, which in turn affects a person's interaction with the environment and social role.
People with AMD usually do not receive medical interventions. Some interventions such as antioxidant vitamin and mineral supplementation may be beneficial in stopping the progression of AMD, but there is not yet supporting evidence of this.31 Rehabilitation for AMD focuses on skills training (e.g., use of a long-cane) and environment (usually home) modification (e.g., improved lighting and contrast) as well as social support services.
The research necessary to demonstrate effectiveness is only beginning to emerge for the variety of interventions available for vision rehabilitation. The diagnosis and provision of rehabilitation services remain based upon largely subjective assessments. The need to develop a body of evidence for the effectiveness of technologies and services, including the conduct of outcomes research, has not been sufficiently emphasized in the field of vision rehabilitation. This is due in part to the presence of some forms of vision rehabilitation in both the clinical mainstream and the charitable and social services, and the limited linkages between these sectors.
In its report Vision Research: A National Plan, 1999-2003, the National Eye Institute (NEI) proposes that framing vision rehabilitation as a subspecialty of rehabilitation medicine "may assist in integrating [vision rehabilitation] into mainstream health care, facilitating appropriate reimbursement procedures, and ultimately providing more visually impaired persons with access to rehabilitation services."32 NEI also identified the need to evaluate models of vision rehabilitation to determine their effectiveness for different patient populations.32
Only recently have incentives been put into place by payers and providers, including the Department of Veterans Affairs (VA), for requirements for professional certification and accreditation and for documented, demonstrated effectiveness of services. For example, services funded under the Rehabilitation Act of 1973 have not been subject to outcomes standards. The incentives for demonstrating effectiveness may increase due to recent legislation that has proposed Medicare coverage of vision rehabilitation services delivered by physicians, occupational therapists, or vision rehabilitation professionals as physician extenders. Although the unit costs of vision rehabilitation may be low, given the high and increasing prevalence of vision impairment and the aggregate costs could be high. The move towards Medicare reimbursement is likely to emphasize the need to demonstrate the effectiveness and/or cost-effectiveness of vision rehabilitation.
Estimates of the number of people in the United States with visual impairment vary. Based on National Health Interview Survey (NHIS) data, 3 million or more older Americans are visually impaired.33 A 1995 national survey by Lighthouse International found that among a sample of 1,219 people age 45 and over, 17 percent reported a problem with vision, although it is unclear how this was defined.34 This prevalence, projected to over 13.5 million Americans aged 45 and older, is higher than was previously thought. Other surveys report that there are 6.6 million older visually impaired persons, of whom only 1 percent use rehabilitation services.19
Vision impairment is disproportionately prevalent among some racial and ethnic minority groups. The Baltimore Eye Survey, conducted in 1985-88 and based on a randomly selected, stratified, multistage cluster sample of 2,395 African-Americans and 2,913 whites aged 40 years and older in East Baltimore, found that bilateral blindness is far higher among African-Americans than whites.35 In addition, the causes of bilateral blindness differed by race. Whites were more likely to have age-related macular degeneration; blacks were more likely to have primary open-angle glaucoma. Another analysis of these data shows that rates of less severe visual impairment are also higher among African-Americans than whites. Over half of the visual impairment identified might have been improved through surgical intervention.36 According to a survey by Mann et al. (1993, as cited in Williams33), there is a large unmet need for adaptive measures among the visually impaired.
More than two-thirds of individuals with low vision are age 65 and older. As the population ages, the prevalence of low vision is expected to increase. Most older adults with low vision have at least one other physical impairment.20 Vision loss has been found to be associated with higher prevalence of a variety of comorbidities, activity limitations and participation restrictions among the elderly.37 Rudberg et al. (1993, as cited in Stuen34) found that the visually impaired elderly are more likely to suffer disability in ADLs than the non-visually impaired. Therefore, the goals of vision rehabilitation are often intertwined with the goals of geriatric care more generally, including the restoration and maintenance of functional independence; prevention of negative health outcomes; the availability of a range of choices of models of care; and appropriate and acceptable assessment and planning.33 For the elderly population, it is theorized that effective vision rehabilitation could help to prevent associated functional impairments associated with high mortality and acute and chronic morbidity, including falls and hip fractures and accidents while driving.33 Moreover, activity limitations intensified by vision loss, such as decreased physical activity, may have negative implications for long-term health.
Most rehabilitation for low vision entails environmental adaptations and compensatory strategies to help people improve their independent functioning or counseling to address psychosocial aspects of losing one's sight. Optical devices and other assistive technologies can help those who are able to use them. The Lighthouse Handbook38 states that best practices incorporate a range of services, including:
Diagnosis and Assessment
Accurate diagnosis facilitates the prescription of services. Diagnosis may illuminate factors underlying visual impairment; understanding the cognitive, motor, and sensory interactions between vision and functioning can help to target appropriate rehabilitation services.32 Furthermore, diagnosis also is tied to access to services given that the allocation of public benefits and health services planning is typically based upon clinical measurement.39
There exist a variety of authoritative recommendations regarding the diagnosis (and screening) of vision impairment, such as including visual assessments in general assessments (particularly among the elderly) and training general assessors in the availability of vision rehabilitation. However, these are not uniformly based on strong evidence. For example, in an RCT of office-based screening for common problems in older persons, family physicians and internists who were provided specific screening information were not more likely to detect visual impairment compared to those in a control group that was not provided with this information, although they were more likely to detect hearing impairments.40 This may have been due to the lower sensitivity of the screening tool used in the RCT (the MOS SF-36) to vision impairments compared to hearing impairments.
In a study not published in the peer-reviewed literature, Horowitz et al. reported on a quasi-experimental design in which one nursing home served as the intervention site receiving a three-pronged intervention and a second nursing home served as a comparison site. The intervention strategy involved three main elements:
In this study, the staff training intervention did not emerge as superior for correctly identifying residents with visual problems. In the comparison of effectiveness in providing corrective refraction services, many more intervention site residents were recommended for new refraction than those in the comparison site. However, this comparison was flawed, as the intervention site relied on an optometrist who was aware of the project goals and tended to look for refractive errors, while the comparison site had an ophthalmologist who apparently was not as involved in the project and tended to look for medical disorders of the eye rather than refractive errors. Further, the optometrist was more inclusive in referring visually impaired residents for vision rehabilitation services (i.e., referred more patients who were less visually impaired) than the ophthalmologist, who tended to reserve such referrals to more seriously visually impaired residents. While there were selective improvements in patients who were referred for low vision clinical and rehabilitation teaching services, the comparisons of the impact of these interventions on any outcomes were flawed by the referral process.41
Although ecological evaluations (i.e., evaluations in which the rehabilitation professional observes the client in his or her own surroundings) are recommended, the effectiveness of this intuitively appealing method of assessment remains to be substantiated with evidence.42
Entry into the system for vision rehabilitation often occurs through referral from ophthalmologists, optometrists, or through outreach in schools for children.42 The literature calls for providers outside of the vision specialties, particularly geriatricians and nursing home staff, to recognize and address vision loss. However, identifying individuals in need of vision rehabilitation services will remain a significant challenge in this field, and is subject in part to further development, validation, and recognition of instruments to assess vision impairment and related functional status. A few validated instruments exist for the assessment of functioning and satisfaction, and some newer ones have been tested recently, yet no definitive set of instruments is widely used. Instruments include, but are not limited to, the following.
Other assessment tools may focus on specific instrumental or basic ADLs, such as reading and writing. However, in most cases, rehabilitation teachers use less formal, subjective assessments of their clients' reading and writing ability.27 Though reliable measurement tools for assessing performance in people with non-vision specific disabilities are lacking, some do show promise.
In sum, despite some limited instances of progress, the evidence for the various means of low vision screening, diagnosis, and assessment remains weak. The need for accurate screening and diagnosis presents a challenge to the delivery of rehabilitation services and the eligibility for public benefits. This applies not just to the lack of instruments for measuring vision loss, but to the lack of awareness or reluctance of people at risk for low-vision to be screened or diagnosed.
Assistive Technologies and Skills Training
Some medical interventions, including laser photocoagulation, vitreous surgery, and cataract surgery with lens implantation are effective in preventing blindness and/or improving vision among certain indicated patients. However, rehabilitation for individuals with low vision focuses on services for individuals without medical options.
The rehabilitation literature outside of the field of vision impairment indicates that the use of assistive devices can have positive effects.42 Persons with nonvision disabilities who use such devices can be more independent,55 and devices can mitigate the effects of disabilities.56 For people with low vision, a variety of optical and electronic aids may help to carry out everyday activities. In general, optical aids enhance vision in two main ways: through magnification or vision field enhancement.
A 2-year study of veterans who received low vision devices from the VA found that subjects reported the devices to be beneficial, and they used them for a variety of tasks.57 The selection of aids depends on the underlying cause of visual disability, personal preference, and other factors. A single device will usually not meet the needs of all tasks likely to be encountered. Categories of optical devices used in the field of low vision rehabilitation include:58,59
According to the American Occupational Therapy Association, training in the use of optical devices is needed for optimal effectiveness.28 When 125 patients received simple low-vision aids with emphasis on training in their use, self-reported satisfaction and use of the aids was higher compared to patients who received the aids without training.60 In addition, instruction in eccentric viewing (utilizing a portion of the peripheral retina for tasks such as reading and mobility) and page-orientation techniques may also be useful. Alternative methods of reading include Braille (or electronic Braille displays), electronic reading stems which enable printed text to be synthesized into speech, audiotapes, and reader services.21,28 It is unclear how frequently these alternative methods are used; Lighthouse International estimates that fewer than 10 percent of the legally blind in the United States read Braille.61
It is notable that training is not limited to practical device use or daily living skills. Training may also occur at the basic perceptual level. For example, peripheral vision training can aim to compensate for lost central vision. The effectiveness of the different categories of training is not yet known. However, there is general consensus among the expert advisors for this study that training is critical.
Non-optical devices and techniques that can help improve the daily functioning of these individuals include:59
Other techniques to improve the use of residual vision include lighting optimization and contrast enhancement. Although illumination levels will be based on personal preference, there are some general guidelines. For example, the light for detailed close work is best provided when it is directed from behind the person, decreasing potential glare. Also, directional lighting (e.g., with a gooseneck lamp) is useful for lighting a task without shining light into the person's eyes. Dimmer switches allow for varying levels of illumination depending on the task at hand. Halogen lamps, which provide more intense illumination, are helpful for individuals with AMD. Contrast enhancement can be accomplished by adequate lighting or electronic magnifiers as well as proper selection of writing and reading materials (e.g., bold-print media, black ink on white paper).21
The four most common systems used to enhance orientation and mobility skills are functional vision, a human guide, a long cane, and a dog guide. Other techniques include "walking along," which refers to following an environmental feature, such as a curb. Electronic travel aids (ETAs), which emit light or sound, may be included in the list of orientation and mobility systems. However, there are several obstacles to greater use of ETAs. They are currently expensive, require significant training, and may provide insufficient amounts of information to the user (e.g., they often cannot detect changes in surface levels such as a curb). Electronic aids that use digital and satellite navigation intended for orientation in larger space have not yet been widely adopted.62 Typically, individuals use functional vision and one of the other systems to enhance their orientation and mobility skills, or they use a system (such as a human guide) selectively. It is important to point out that the evidence base for orientation and mobility training is weak. There has been very little research on the short- or long-term effectiveness of orientation and mobility techniques or on the degree of safety they offer.26
There is limited though generally inconclusive evidence differentiating the effectiveness of some low-technology interventions. For example, half-field eye patching for unilateral spatial neglect has been shown in an RCT involving 22 subjects to significantly improve functioning to a greater extent than does monocular patching.63 The effectiveness of a given device may differ depending on the cause of low vision. For example, persons with restricted visual fields are least served by available devices, and devices for increasing field awareness have not been shown to be effective.32
Whether for society at large or for people with low vision in particular, technological advances have both undesirable and desirable effects. Negative outcomes occur when technologies raise barriers to entry in the workforce by eliminating low-skilled jobs, changing the nature of work, or when individuals may benefit from a technology, but lack access to it.64 One example of a negative impact of advanced technology on people with low vision is the widespread use of graphic user interface (GUI) software for computing. Whereas computers based on DOS were relatively easy to modify for use by the visually impaired, Windows® or other graphic systems are difficult to convert into audio or Braille text. In addition, as telecommunications become more oriented to visual media, barriers will be created for the visually impaired. On the other hand, the use of voice in technological devices will increase access, allowing the visually impaired to use telecommunications even for the interpretation of face-to-face interaction.65 This is possible due to advances in electronics and voice technology, and network-based services that translate information across communication modes (e.g., voice descriptions of visual information). Such technological promise notwithstanding, it is likely to be necessary to demonstrate the effectiveness of these advances for the visually impaired in order to secure third-party payment for them, where applicable.
A growing number of evolving optical and non-optical aids and techniques are available to enhance the daily functioning of individuals with vision impairment. The literature highlights the importance of the user-technology interface and emphasizes the importance of matching the device and technique to the needs of the individual. In addition to clinical medical evaluation, this includes consideration of social, psychological, familial, financial, and other factors. Technical factors to be considered in the selection of optical devices include power, working distance, working space, field of view, light, focal length, depth of field, and light transmission.59 However, despite the availability of these technologies and the consensus regarding the need to match them to user-specific needs, there is no clear-cut evidence concerning which devices and techniques are beneficial to people with particular impairments.
Environmental Modifications and Compensatory Strategies
Environmental modifications are used to improve the independent functioning of people with low vision. The American Occupational Therapy Association and others recommend that therapy sessions for those with visual impairment be provided within the environment where they will be, including home, community, and workplace.28 Perhaps because these interventions can be quite individualized, there do not appear to be controlled trials of their effectiveness. Further, because these low-cost technologies have not typically been subject to reimbursement, third-party payers have not been leading the call for strong evidence in their support.
Many environmental interventions comprise simple, "low-tech" approaches. For example, for users that have difficulty with stairs because of reduced contrast between the risers, a line of fluorescent tape or paint at the edge may help distinguish the steps. Increasing illumination, as discussed above, may help individuals see objects and people more clearly. If these means fail to achieve the desired outcome, compensatory techniques can be developed. For example, if an individual cannot see to thread a needle, he or she may be able to feel a needle threader. Similarly, if an individual cannot read a stove dial, a tactile mark can be used to indicate the proper setting. Hearing is used to monitor traffic at intersections, and smell is used to identify foods.28 The effectiveness of these types of aids, techniques, and compensations will likely depend on the individual and his or her goals for independence. Examples of adaptive equipment for individuals with low vision are:21
The low cost of many of these techniques may be an important factor in an individual's decision to employ some of these interventions instead of the more expensive optical devices discussed above, especially considering the financial barriers faced by many individuals with disabilities, including those with low vision.