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Vision Rehabilitation

August Colenbrander, MD

Vision is the most important source of information about our environment. Loss of vision reduces the ability to perform activities of daily living, and affects safety and quality of life. Most of this book deals with reducing the causes of vision loss. Vision rehabilitation deals with reducing its consequences.

In developed countries, and increasingly in developing countries, the majority of irreversible vision loss occurs in the elderly and will represent an ever increasing part of ophthalmic practice (see Chapter 20). Unfortunately, many patients and caregivers still consider vision loss as an inevitable result of aging and often do not seek the help that is available. It is the task of the ophthalmologist to tell them that even if “nothing more can be done” about their reduction of vision, “much can be done” to deal with the consequences of vision loss for the person.

STAGES OF VISUAL PROCESSING

When dealing with the consequences of vision loss, it is important to recognize that vision is a complex, multistage process. Dysfunction at the different stages of visual processing causes different problems that require different solutions. The first is the optical stage, which puts an image of the outside world on the retina. The second is the receptor stage, which translates the optical image into neural impulses. The third stage is neural processing, which starts in the inner retina and proceeds via the visual cortex to higher cortical centers, where it eventually gives rise to visually guided behavior.

The optical stage can be disrupted by refractive errors and media opacities. Letter chart acuity is a good tool to evaluate this stage, and magnification devices (see Chapter 24) are the natural choice to counteract this type of vision

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loss.

The receptor stage can be disrupted by retinal disease. If foveal function is reduced, visual acuity is reduced. If foveal function is absent, causing a central scotoma, a pseudo-fovea or preferred retinal locus (PRL) must take over fixation. This eccentric area will have a reduced receptor density, which causes further reduction of visual acuity.

For retinal disorders, letter chart acuity is important but tells only part of the story, since it describes only the function at the point of fixation and tells us nothing about the condition of the surrounding retina (even a 20/200 letter covers less than a 1° area). Normal vision involves constant eye movements, which may move the object of attention in and out of the best-functioning area. This scotoma interference, which may be apparent as hesitation during testing, is not quantified by visual acuity and cannot be remedied with magnification devices. Patients need training and practice to improve their fixation stability. This may be provided by occupational therapists or vision rehabilitation specialists, but it is up to ophthalmologists to recognize the need for this training and to make the appropriate referral.

Neural processing comprises the third and most complex stage. Awareness of vision problems related to the processing of visual information is increasing. It includes the perceptual consequences of traumatic brain injury (TBI) in adults, cerebrovascular accidents (CVAs) in the elderly, and cerebral (cortical) visual impairment (CVI) in children. In this area, the ophthalmologist may need to cooperate and communicate with social workers and educators.

Some cerebral defects produce obvious impairments of visual acuity and visual field (visual impairment). More subtle defects (visual dysfunction) may exist in the presence of normal performance on standard clinical testing. A patient with optical or retinal problems may stumble over a curb because of lack of contrast, whereas a patient with a cerebral injury may be able to detect the change in contrast but may be unable to decide whether this is a line on the ground or the edge of a step. In this case, vision enhancement (better illumination, contrast) will not help, and vision substitution (use of senses other than vision such as a cane to tactically determine the step) may be more appropriate. Full assessment of impaired cerebral processing may involve other professionals and neuropsychological testing, but preliminary assessment by ophthalmologists can often be the starting point.

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ASPECTS OF VISION LOSS

A convenient framework to discuss the various impacts of vision loss considers four aspects of visual functioning: organ structure, organ function, individual abilities, and societal consequences (Figure 25–1).

Figure 25–1. Aspects of vision loss. ADLs, activities of daily living.

Macroscopic and microscopic examination of tissues may reveal structural changes, such as scarring, degeneration, and atrophy. This is the domain of the ocular pathologist. But these changes do not necessarily indicate how well the organ functions. To assess this, we need tests, such as visual acuity, visual field, and contrast sensitivity, which determine organ function. This is the domain of the ophthalmologist. However, “how well the eyes function” does not yet assess “how well the person functions” in performing various activities of daily living (ADL) and various visual abilities, such as reading, getting around, or recognizing faces. This is the domain of occupational therapists and other rehabilitation professionals, who need to work with patients and teach them how to use their residual vision most effectively. Finally, there is a need to assess how these changes affect the person’s role and participation in society, since this is the ultimate goal of all interventions at whichever level. From this short summary, it should be clear that comprehensive vision care cannot be the work of one person; it requires team work, and the patient needs to be a part of this team.

Traditional textbooks describe these four aspects from left to right in the sequence from causes to consequences. For patients, however, the starting point is on the right, since they experience primarily the societal consequences. The patient may come with a complaint: “Doctor, I cannot read”; the doctor translates this to a statement about the eyes: “She has lost three lines.” The doctor is primarily interested in the “how the eyes function” and wants to find

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and treat the underlying causes; the patient is primarily interested in “how the person functions” and wants to alleviate the consequences. It is the task of rehabilitation to bridge this gap.

Recognizing how doctors and patients approach medical conditions from different points of view is essential for effective communication. Seemingly similar tests may have to be done in somewhat different ways. Clinicians, who are interested in how each eye functions, will measure visual acuity for each eye separately. However, to determine how the person functions, whether for employment, for a driver’s license, for education, or simply for quality of life, we must measure visual acuity with both eyes open, since that is how people live their lives. Although we have two eyes, those eyes are part of a single visual system that generates a single visual perception. This shift in emphasis was explicitly recognized by the World Health Organization in a 2003 consultation, which acknowledged the fact that health statistics are not only a tool to detect eye disease, but also to describe the burden of vision loss in a population. At the individual level, this is also important. Refractive surgeons are becoming increasingly aware of the need to individualize treatment to the patient’s needs. A comprehensive reading assessment should not only determine the smallest print size read, but also reading speed, reading endurance, reading enjoyment, and reading comprehension.

COMPREHENSIVE VISION REHABILITATION

Considering all of these aspects, it should be clear that comprehensive vision rehabilitation extends beyond the provision of low-vision aids, although that is still vitally important (see Chapter 24). Since any rehabilitation requires teamwork involving different professionals to deal with the various components and since vision loss is the common denominator, the ophthalmologist should coordinate the team.

History and Goal Setting

Before considering a rehabilitation plan, the patient’s goals and needs must be clarified. For the general ophthalmologist, this may involve only a general question, such as, “How does your vision loss bother you most?” or “Can you still read the newspaper?” If the answer reveals a problem, clinicians should do

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the same as they do for retinal, glaucoma, or other problems and tell the patient,

“I understand your problem and I will refer you to someone who can help you.”

When future deterioration is a possibility, it is not necessary to wait until there is severe vision loss before recommending action. Early adaptations to minor loss can facilitate later adaptations to major loss. The possibility of deterioration of vision is best made known from the beginning but must be accompanied with advice about the availability of skilled professionals and resources. Unfortunately, many practitioners are poorly trained in conveying bad news, a skill that should be taught and practiced in medical school. All ophthalmologists should master this skill, which includes informing the patient about options and knowing the appropriate referral sources.

The American Academy of Ophthalmology (AAO) recognizes several levels of competence in vision rehabilitation. Some ophthalmology practices may employ professionals who can provide basic services in-house. For more complex cases, referral to specialized vision rehabilitation services is appropriate.

To determine the range of services that are appropriate, the AAO recommends the following checklist:

•Reading—For many patients, this is their foremost concern.

•Activities of daily living (ADLs)—Even though reading may be the most prominent complaint, most people spend the larger part of their day performing a variety of other activities.

•Safety—Are people at risk for falls? How do they cross the street?

•Community participation—Can they still participate in community events or at church?

•Physical, cognitive, and psychosocial well-being—Since many patients with vision loss are elderly, this is an important aspect that should not be overlooked. If problems exist, they may affect the recommendations to be made.

Not all areas may have problems, but the simple 5-point checklist is important so that priorities can be set and specific rehabilitation goals formulated that reflect the patient’s needs and desires, not just the practitioner’s expectations.

Examination

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The standard ophthalmic examination, including identification of any conditions amenable to specific treatment, needs to be adapted as discussed in Chapter 24.

Observation of visual performance is important in young children, where regular testing may not be possible. Reports from parents and teachers are often as informative as direct observation in the office. Even for adults, observation of the performance of daily living tasks can be helpful. It provides a baseline against which future progress can be measured. It can also give insight in the patient’s problem-solving skills and motivation.

Questionnaires can assess the subjective difficulty of tasks, including those that cannot be assessed in the office. A disadvantage is that the responses are subjective, with some patients exaggerating their difficulties and others understating them.

Assessment of mobility, including identification of peripheral visual field loss, is very important since impaired mobility should trigger referral for assessment by an orientation and mobility (O+M) instructor. Mobility training may be crucial to reestablishing independence. Patients also need to be made aware of the importance of appropriate signaling of their visual impairment. Many feel that carrying a long cane or similar aid publicizes their vulnerability to individuals who might take advantage of it, but well-meaning individuals need to be made aware of the patient’s visual impairment, so that they can provide assistance where needed.

Comprehensive Rehabilitation Plans

A comprehensive vision rehabilitation plan requires attention to more than just how the eyes function. Figure 25–2 provides a summary of the possible interventions. It is useful to use this as a checklist, although not all parts will be needed in every case.

Figure 25–2. Comprehensive rehabilitation.

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Vision Enhancement (See Chapter 24)

•Vision substitution refers to the use of senses other than vision. Common examples include talking books and voice-output devices (see Chapter 24), Braille, and long canes. Vision enhancement and vision substitution are not mutually exclusive but complementary. A patient may use a magnifier to read price tags and talking books for recreational reading. A patient with retinitis pigmentosa, who has normal mobility in the daytime, may need a cane at night. Audio cassettes may have Braille labels.

•Assistance is a form of vision substitution using the eyes of others. Family members, caregivers, and office personnel should be familiar with sightedguide techniques to effectively assist visually impaired patients with minimal embarrassment. Guide dogs are another possibility. They require training of the dog as well as of the patient, who needs to be physically active and able to manage the dog.

•Coping skills: Vision loss often causes reactive depression, which renders the patient less receptive to rehabilitative suggestions. Conversely successful rehabilitation can be therapeutic and motivate the patient to pursue further improvements. Dealing with severe depression may involve other professionals, but the authority of the ophthalmologist can play a major role in convincing patients that they can do far more than they may believe after the initial shock of vision loss.

•Human environment: As patients go through the stages of adaptation to vision loss, a supportive home environment is essential, and it is important to include spouses, children, and significant others in the counseling process. The clinician should make sure that the significant others understand the underlying condition, what can be expected, and how to support the patient. Answering their questions directly, by having them attend the examination, is often better than leaving this to the patient, who initially may not have absorbed everything that was said. An overprotective environment that deprives patients of opportunities to do things themselves can be as detrimental as an overdemanding one that puts too much emphasis on the patient’s shortcomings. The same applies to work, school, and social groups. Initially, patients often feel isolated and believe that they are the only ones experiencing these problems. This is where peer support groups can be helpful; in these groups, they can experience how others are dealing with similar problems.

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• Physical environment: An uncluttered environment, where things have a defined, fixed place is helpful because it eliminates the need for searching. Good general illumination and task lighting often help, because at higher illumination levels retinal cells that are damaged but not dead can still contribute. Good contrast is important; for instance, milk should not be served in a white Styrofoam cup and edges of steps and stairs should be marked.

CONCLUSION

The patient’s life does not end with the diagnosis of visual impairment. Similarly, the responsibility of the ophthalmologist does not end with the treatment of eye disease, but extends to counseling the patient and initiating rehabilitation, based on knowledge of the available resources and referral pathways.

RESOURCES

Searching business telephone directories (yellow pages) and the Internet under visual impairment, low vision, blindness, and rehabilitation can provide useful information on local rehabilitation resources.

General Information

The SmartSight initiative of the American Academy of Ophthalmology (www.AAO.org, search SmartSight) contains handouts for patients as well as for practitioners (including an extensive list of resources).

The American Foundation for the Blind (www.AFB.org/) contains many resources for various age groups and conditions.

The MDsupport website (www.MDsupport.org) specializes in support for age-related macular degeneration.

The Lighthouse International in New York (www.lighthouse.org) offers extensive resources for all forms of vision loss.

These websites contain links to many more websites with additional

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information and often can provide information about local resources.

Personnel

Occupational Therapists (OT) (www.aota.org). This profession evolved in the health care field. They have broad rehabilitation training, but traditionally learned little about vision. This is changing as the demand for vision rehabilitation grows.

Another group includes Certified Low Vision Therapists (CLVT), Certified Orientation and Mobility Specialists (COMS), and Certified Vision Rehabilitation Therapists (CVRT). These professions evolved from the education field. Their training is vision-specific, but traditionally focused on students and younger age groups. They are certified by the Academy for Certification of Vision Rehabilitation & Education Professionals (www.acvrep.org).

For both groups, their state chapters may provide information about available manpower.

Devices, Technology

Low-tech devices, such as magnifiers and telescopes, are available from many suppliers, who have their own websites. They are relatively low cost and can serve a large number of patients. High-tech devices, such as video-magnifiers, cost more and evolve more rapidly. For these, it is important to get up-to-date information from a specialist (see Chapter 24).

The Library of Congress provides an extensive library of free talking books.

Financial Support, Social Services

Financial support and social service programs may vary from state to state. All states have vocational rehabilitation programs. Special services are available for veterans through the Veterans Affairs Blind Rehabilitation Centers. Local agencies are often the best source of information.

REFERENCE

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Consultation on Development of Standards for Characterization of Vision Loss and Visual Functioning. WHO, Geneva, 2003. Available at http://apps.who.int/iris/bitstream/10665/68601/1/WHO_PBL_03.91.pdf.

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APPENDIX

Functional Vision Score

August Colenbrander, MD

HISTORY

Vision loss is a complex phenomenon that cannot be fully understood unless many different aspects are considered (see Chapter 25). Yet, for certain applications, it may be desirable to reduce this complex reality to a single number. Administrators prefer the oversimplification of the single number approach when they have to decide on eligibility for benefits or for worker's compensation cases, where the outcome also is a single number: the amount of compensation.

Formulas to calculate what was then called “Visual Economics” were first proposed in Germany in the late 1800s. In 1925, Snell proposed to the American Medical Association (AMA) a simpler formula for “Visual Efficiency.” This formula, reflecting an 80% loss of employability for a visual acuity loss to 20/200, served until 2000. In its fifth (2001) and sixth (2008) editions the AMA

Guides to the Evaluation of Permanent Impairment adopted the “Functional Vision Score” (FVS), which reflects an estimate of the ability to perform activities of daily living (ADL).

On the new scale, 20/200 acuity is rated as an estimated 50% loss of ADL ability, rather than as an 80% loss of employability. Other changes include no longer considering the two eyes as separate organs, vision with both eyes open being the normal condition. The new scale has been shown to correlate well with other measures of ability.1

CALCULATING THE FUNCTIONAL VISION SCORE

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Figure A–1 represents the steps in calculating the functional vision score and its use in calculating an AMA impairment rating.

Figure A–1. Steps in calculating the Functional Vision Score (FVS) and the AMA impairment ratings.

Functional Acuity Score

The first step is measuring the visual acuity. Use of an ETDRS-type chart with a logarithmic progression of letter sizes and five letters on each line is preferred. The best corrected acuity is measured for each eye and with both eyes open.

According to the Weber-Fechner law, visual ability is proportional to the logarithm of the visual acuity value. This is reflected in the visual acuity score (VAS) (Table A–1). On an ETDRS-type chart, the VAS increases by 1 point for every letter read correctly; the scale is anchored at 20/20 = 100.

Table A–1. Visual Acuities (VA), ETDRS Letters (ETDRS), and Visual Acuity Scores (VAS)

Next, the three VAS values—both eyes (OU), right eye (OD), left eye (OS)—are combined to provide a single functional acuity score (FAS), with 60% weighting being given to the acuity with both eyes open and 20% to each of the

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monocular values.

Functional Field Score

In a similar way, a visual field score (VFS) and functional field score (FFS) are calculated. The VFS is determined with a grid (Figure A–2) that allocates 50 points to the central 10° (radius) area and 50 points to the remainder of the visual field reflecting the representation of the central 10° of visual field over about 50% of the primary visual cortex. It also divides the score evenly between the central area, which is important for reading and detailed vision, and the outer area, which is important for orientation and mobility.

Figure A–2. Visual field score grid, showing the total number of points in each region (left half) and how the points are allocated along the five meridians (right half). The radius of the circle is 10°.

The points are allocated along two meridians in each of the upper quadrants and three meridians in each of the lower quadrants. On each meridian, 5 points (2° apart) are assigned to the central area and 5 points (10° apart) to the outer area, with their distribution being approximately logarithmic. The lower visual field is weighted 50% more than the upper visual field because of its greater importance in functional vision. The primary meridians are not used, to avoid the need for special rules for hemianopias.

The VFS is determined by counting the number of points seen within the visual field delineated by the Goldmann III4e (or equivalent, eg, Humphrey 10 dB) isopter. The FFS is calculated from the three VFS values using the same weighted formula for calculating the FAS from the three VAS values (60% OU + 20% OD + 20% OS).

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Finally, the FAS and FFS are combined into a single functional vision score (FVS). Thus far, the calculation follows strict mathematical rules. If there are other vision problems that are not reflected in a visual acuity or visual field loss, the examiner may apply an adjustment of maximally 15 points. Such an adjustment must be properly argued and documented.

CALCULATING THE AMA IMPAIRMENT RATING

The FVS reflects visual function (20/20 = 100), whereas the AMA impairment rating reflects loss (20/20 = no loss = 0). Therefore, the AMA impairment rating is calculated by subtracting the FVS from 100.

Furthermore, a distinction is made between visual system impairment (VSI) and whole person impairment (WPI). One hundred percent VSI (total blindness) does not equal 100% WPI (death). Therefore, a gradual correction is made from VSI = 50% to VSI = 100%, so that 100% VSI = 85% WPI. This adjustment is justified by the increasing use of visual substitution skills (see Chapter 25) at lower visual acuity levels.

If there are impairments in other organ systems, these may be combined (through special tables) with the visual WPI percentage.

For a more detailed discussion with examples, the reader is referred to the AMA publication: Rondinelli RD (ed). Guides to the Evaluation of Permanent Impairment, 6th edition. American Medical Association, 2008.

1Fuhr PSW et al. The AMA Guides Functional Vision Score is a better predictor of vision-targeted quality of life than traditional measures of visual acuity or visual field extent. Vis Impairment Res 2003;5:137.

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