Service delivery is the provision of hard and soft assistive technologies to the consumer. In Chapter 1 we delineated the components of the assistive technology industry, which has at its core the consumer and service delivery programs. This chapter describes the process by which the consumer obtains assistive technology devices and services. Chapter 2 described a model that is used as the basis for assistive technology assessment and intervention (the Human Activity Assistive Technology [HAAT] model) and it discussed the principles of assistive technology system design. This chapter builds on the HAAT model by delineating systematic methods of assessment and intervention that help the team utilize components of the model and integrate them into an effective assistive technology system for each individual consumer. This chapter provides information on the full range of service delivery aspects, highlighting those elements in which the rehabilitation assistant has a primary role. To effectively provide these services to the consumer, the rehabilitation assistant should be knowledgeable in the following areas:

1. The principles related to assessment and intervention and methods of gathering and interpreting information.

2. The service delivery practices used to determine the consumer’s needs, evaluate his skills, recommend a system, and implement the system.

3. The measurement of outcomes of the assistive technology system that indicate whether the identified goals have been achieved.

4. The identification and attainment of funding for services and equipment.

Principles of assistive technology assessment and intervention

The assistive technology intervention begins with an assessment of the consumer. Through this assessment, information about the consumer is gathered and analyzed so that appropriate assistive technologies (hard and soft) can be recommended and a plan for intervention developed. Information is gathered regarding the skills and abilities of the individual, the activities she would like to perform, and the contexts, including social, physical, and institutional elements, in which she will be performing these activities. The assessment also yields information regarding the consumer’s ability to use assistive technologies. Based on the assessment results, a plan for intervention is developed. This plan includes recommendation and implementation of the system, follow-up, and follow-along. Basic principles that underlie assessment and intervention in assistive technology service delivery are listed in Box 3-1.

Box 3-1 Principles of Assessment and Intervention in Assistive Technology

• Assistive technology assessment and intervention should consider all components of the HAAT model: the human, the activity, the assistive technology, and the context.

• The purpose of assistive technology intervention is not to rehabilitate an individual or remediate impairment, but to provide assistive technologies that enable an individual to perform functional activities.

• Assistive technology assessment is ongoing and deliberate.

• Assistive technology assessment and intervention require collaboration.

• Assistive technology assessment and intervention require an understanding of how to gather and interpret data.

Assistive Technology Assessment and Intervention Should Consider All Components of the HAAT Model: Human, Activity, Assistive Technology, and Context

Often AT assessment focuses on the assistive technology only, which can lead to later rejection or abandonment of the technology. One way to reduce the probability of abandonment or misuse is to consider systematically all four parts of the HAAT model. Needs and goals are often defined by a careful consideration of the activities to be performed by the individual. However, it is rare that the activity will be performed in only one context, so it is important to identify the influence of the physical, socio-cultural, and institutional elements in the contexts in which the activities will be performed (see Chapter 2). Thus the careful evaluation of the activities to be performed and the contextual factors under which that performance will occur are keys to success. Once the goals have been identified, an assessment of the skills and abilities of the human operator (the consumer) must be identified. Only after consideration of these three components (activity, context, and human) can a clear picture emerge of the assistive technology requirements and characteristics. The assessment process must also include an assessment of the degree to which these characteristics match the consumer’s needs. Chances of success in implementation of an assistive technology system are enhanced by attention to all four parts of the HAAT model during the service delivery process.

Assistive Technology Intervention Is Enabling

The primary purpose of assistive technology intervention is not remediation or rehabilitation of an impairment, but provision of hard and soft technologies that enable an individual with a disability to be functional in the activities of daily living. This principle places the focus on functional outcomes. Through the application of the HAAT model we can develop goals for the assistive technology intervention, and these goals ultimately are used to measure the functional outcomes of the intervention. Approaching intervention from this perspective requires that the team determines the individual’s strengths and capitalizes on them instead of focusing on deficits or impairments. For example, consider the functional activity of computer input. If we were to use a rehabilitation approach, the goal would be to improve hand and finger control sufficiently to allow for input, with the intervention focusing on exercises and activities for the fingers and hands. From an assistive technology perspective, however, the objective becomes enabling the person to perform the functional activity of computer input using available motor abilities. The impairment in the hands and fingers that causes the disability is not necessarily addressed. The disability of being unable to use a computer keyboard is what is addressed in the assistive technology approach. Through the use of assistive technology, alternatives to the typical way of using the fingers for input, such as using a mouthstick, head pointer, or a speech recognition system, are considered.

This focus on function does not mean that an individual’s potential for improvement is ignored. The parallel interventions model^1,⁴⁴ demonstrates how technology can be used to promote the dual objectives of enabling function and improving an individual’s skill level. In one track, assistive technologies are provided that are based on the consumer’s current skills and needs in order to maximize his function. Simultaneously, a second track provides intervention that focuses on improving his skill level so as to minimize his reliance on technology. Some individuals who have a severe physical disability may have never had the opportunity to develop their motor skills, and training to develop these skills can take months or years.⁸ A common example is an individual whose evaluation shows that she is able to use her head to activate a single switch to make simple choices on a computer. With training and a period of experience in using this switch, her head control may improve to the point where she can use a light beam positioned on her head to make direct choices with a dedicated communication device. The latter means of control provides access that is faster and much less demanding cognitively.

Assistive Technology Assessment Is Ongoing and Deliberate

Although assessment is typically considered a discrete event in the direct service delivery process, it is actually an ongoing process. Assistive technology assessment entails a series of activities linked together and undertaken over time. The activities that occur and the decisions that are made during the intervention are deliberate rather than haphazard. Information is gathered and decisions are made from the moment of the initial intake referral through follow-along.

Progression toward the goals of the intervention plan is ongoing, with revisions to the plan as necessary. For example, during training, observation may reveal that the consumer can access the control interface more effectively if it is positioned at an angle instead of flat. This observation will result in adjustment to the position of the computer interface. The ideas of client-centered practice highlight the importance of involving the client at all stages of assessment, from the initial framing of the activities in which the client wishes to engage to the recommendation of an AT system.⁶ The client refers to the individual and others in their environment such as family and caregivers.⁶ Assessment is ongoing not only while the consumer is actively involved in the service delivery process, but also potentially throughout the consumer’s life. Because many individuals have lifelong disabilities, they will be in need of assistive technology throughout their lives. It is important not only to recommend assistive technology that enables the individual today but also to predict the technology that will be necessary to enable the individual in the future. The components of the HAAT model change over each individual’s lifetime. Changes may occur in the individual’s skills and abilities, life roles, and goals; in the capabilities of technology; and in the context in which the assistive technologies are used. Using the HAAT model as a framework, the team can predict some of these changes and plan for the consumer’s future technology needs.

Assistive Technology Assessment and Intervention Require Collaboration and a Consumer-Centered Approach

Given the nature of assistive technology and its impact on the consumer’s activities of daily living, it is essential that the assessment and intervention be a collaborative process. McNaughton (1993)³¹ defines a collaborator as “one who works with another toward a common goal” (p 8). Furthermore, she states that collaboration requires that (1) all participants be equal partners; (2) a problem-solving attitude be shared by all participants; (3) there be mutual respect for each other’s knowledge and the contributions each person can make, as opposed to the titles he or she holds; and (4) each participant has available the information necessary to carry out his or her role.³¹ These ideas are supported in the ideas of client-centered practice.⁶

There are several people who are key collaborators in the assessment and ongoing evaluation process. Central to this group is the consumer who will be the primary user of the technology and his caregivers/family who will be assisting with care and use of the technology on a regular basis. Other collaborators include teachers, vocational counselors, employers, therapists, and representatives from the funding source. The assistive technology assessment and intervention is more successful when these significant others are identified and involved at the beginning of the process.

There is a delicate balance between the “opinion” and “expertise” of the team (based on technical knowledge and experience with a variety of individuals) and the “opinion” and “expertise” of the consumer and family relating to their specific needs and goals. The consumer and family come to the assessment process with expertise in their daily lives, including the activities in which they need and want to engage, as well as expertise in the modifications and strategies they employ in the performance of these activities. The role of the team is to educate the consumer on the choices available to her so that she can make decisions related to the assistive technology in an informed manner. The challenge for the ATP is to do so without unduly influencing her choice. As identified above, AT is one component of the process of enabling activities. It may not be the consumer’s preferred method of performing activities. Beukelman and Mirenda (2005)⁴ discuss the importance of building consensus among the user, family members, and other team members. Negative consequences—such as a lack of vital information needed for the intervention; lack of “ownership” of the intervention, resulting in poor follow-through with the recommendations; and distrust of the service provider—may result if the process of consensus building is not begun during the initial assessment. Initiating this process early on helps to avoid problems in the future with regard to the acceptance and utilization of a device.

Assistive Technology Assessment and Intervention Require an Understanding of How to Gather and Interpret Data

The assessment process (either initial or ongoing) involves determination of what needs to be assessed and the most effective method of completing the assessment. It occurs in both formal and informal manners, using a variety of methods. Commonly, formal assessments involve use of standardized instruments, following the protocol established by the instrument developers.³² Informal assessment tends to occur on an ongoing basis, often involving observation or interview as the client is engaged in daily activities. Assessment includes gathering information on the client’s physical, sensory, language, and cognitive skills and emotional state; his performance in functional activities; the details of the settings in which these activities occur, including physical accessibility issues; social support; and institutional elements such as funding and policies around AT use and maintenance in those settings.

The rehabilitation assistant may be involved in the data-gathering process using a standardized assessment providing that she has established competence in the administration of the assessment and that the use of the assessment is not restricted to specific professionals.⁴⁵ For example, some cognitive tests are limited to use and score interpretation by only registered psychologists. More commonly, she will be involved in informal data gathering, particularly during the implementation phase of the AT service delivery process. The data gathered by the rehabilitation assistant provides useful information to guide the device selection process; thus she needs to be able to present her findings effectively in both written and verbal formats.⁴⁵ She also needs to understand issues of measurement to appreciate the implications of the conclusions that are drawn from the data she has gathered.³² A framework to guide this data collection will be presented and discussed later in this chapter. A more thorough discussion of assessment formats, different types of measurements, and data gathering and interpretation follows in the section on initial evaluation of the AT service delivery process.

Overview of service delivery in assistive technology

Figure 3-1 illustrates the basic process by which delivery of services to the consumer occurs. The first step is referral and intake. Referral can be initiated by many different people, depending on the service delivery context. The consumer or a family member, a physician or another health care professional, or a teacher or other professional may make a referral for an AT assessment. The service provider gathers basic information and determines whether there is a match between the type of services he provides and the identified needs of the consumer.

Figure 3-1 Steps in the service delivery process.

Once the criteria for intake have been met, the evaluation phase begins. The first step involves an interview with the consumer and relevant others to identify their concerns about the consumer’s engagement in daily activities, which results in a needs identification. Following a thorough identification of the consumer’s needs, the consumer’s sensory, physical, language, and cognitive skills are evaluated. Technologies that match the needs and skills of the consumer are identified and, ideally, a trial evaluation of these technologies takes place. The evaluation results are summarized and recommendations for technologies are made based on consensus among those involved. These findings are summarized in a written report, which is used frequently to justify funding for the purchase of the assistive technology system.

When funding is secured, the consumer proceeds with the intervention in the implementation phase. At this phase, the equipment that has been recommended is ordered, modified, and fabricated as necessary; set up; and delivered to the consumer. Initial training on the basic operation of the device and ongoing training of strategies for using the device also take place during this phase. The rehabilitation assistant plays a primary role at this phase. Her feedback provides important information in monitoring the successful outcome of the technology use.

Once the device has been delivered and training has been completed, we need to know whether the system as a whole is functioning effectively. This step normally occurs during the follow-up phase, in which we determine whether the consumer is satisfied with the system and whether the goals that have been identified are being met. The follow-up phase actually closes the loop by putting in place a mechanism by which regular contact is made with the consumer to see whether further assistive technology services are indicated. When further AT services are required, the consumer returns to the referral and intake phase, and the process is repeated. Building this final phase into the service delivery process ensures that the consumer’s needs are considered throughout her lifespan. Now let’s take a more in-depth look at each of these steps.

Referral and Intake

The purpose of the referral and intake phase is to (1) gather preliminary information on the consumer, (2) determine whether there is a match between the needs of the consumer and the services that can be provided by the ATP, and (3) tentatively identify services to be provided.¹⁹

The consumer, or the person making the referral on the consumer’s behalf, recognizes a need for assistive technology services or devices, which triggers the referral to the ATP. These identified needs are called criteria for service, and they define the objectives for the intervention. A third-party funding agency, such as a state vocational rehabilitation agency, may be involved at this stage. They will have a set of policies and procedures that governs who is eligible to seek assistive technology intervention and what devices and services they cover. Depending on the policies of the service provider, referrals are accepted from a variety of sources. These sources include the consumer, a family member or care provider, a rehabilitation or educational professional, or a physician. At this time, information regarding the consumer’s background and perceived assistive technology needs is gathered for the initial database. This information includes personal data (e.g., age, place of residence), medical diagnosis and health information, and educational or vocational background. Information related to the individual’s medical diagnosis and health information that may guide the assessment includes whether or not the condition is expected to remain stable, improve, or decline. The appropriateness of the referral is viewed from the perspective of both the ATP and the referral or funding source. When exchanging information about the consumer’s needs and the services provided by the ATP, each party can determine whether there is a match. For example, the needs of a consumer with complex seating and mobility needs may not match the services provided by the ATP if the ATP does not have the necessary expertise in this area. For the consumer’s benefit, this mismatch should be acknowledged and the consumer referred to another source that can more appropriately address her needs. The assistive technology provider should have a policy within the organization’s mission statement that establishes what services are provided and who is eligible to receive those services. For example, some assistive technology service providers specialize in certain disabilities (e.g., visual impairment), and others focus on specific technologies (e.g., seating technologies). Professional codes of ethics and standards of practice (see Chapter 1) require that ATPs practice within their specialization and not try to provide services outside of this realm.

The other outcome is that there is a match between the needs of the consumer and the services provided by the ATP. In this case, plans are made to move forward with the initial evaluation, starting with a thorough identification of the consumer’s needs. In some jurisdictions funding must be secured prior to the initiation of the evaluation. From the information provided, the ATP also determines the level of service that would be most beneficial to the consumer. There are a number of scenarios. First is the individual who has never used or been evaluated for assistive technologies, which could be an individual who is newly disabled or someone with a long-standing disability. An individual with a long-standing disability who may not have previously received assistive technology services may now be able to access assistive devices because of recent advances in technologies. In this situation an in-depth assessment is warranted. Referrals may also be received from consumers who have used assistive technology for some time and would like to evaluate current commercially available technologies. If this person’s functional status has remained stable, it may not be necessary to conduct a complete evaluation. In some cases the assistive technology is not working or has been abandoned by the consumer and he is seeking a referral to see if modifications to the system can aid in making it more functional. Sometimes the consumer may only require further training or reevaluation of how she is using her current system to see whether training in new strategies would be beneficial. Similarly, there may be a new care provider who needs training or technical assistance.

Initial Evaluation

Through a systematic evaluation, the ATP gathers information and facilitates decisions related to eventual device use. Because of the cost of the assistive technology to the consumer (or third-party funding source), it is essential that the team be able to assist the consumer in making informed decisions in the selection of a device. Current knowledge of the available technology and use of a systematic process facilitate the decision-making process. This section focuses on the type of information gathered and the procedures used during the evaluation. We start with some background information on measurement.

Quantitative and Qualitative Measurement

Throughout the assistive technology intervention, the team can gather information by either quantitative measurement or qualitative measurement. The philosophies of qualitative measures and quantitative measures are quite different. Quantitative measures assign a number to an attribute, trait, or characteristic.³⁴ The assumption of quantitative measures is that the construct of interest can be measured in some meaningful way. For example, a test can be constructed that measures the joint range of motion (the construct) available to an individual to control a computer access device. Joint range is expressed as degrees of motion and a common understanding exists regarding what is meant when a specific joint range of motion is described. Here the construct can be assigned a number that is meaningful to individuals both using and interpreting the test. Alternatively, a test can be constructed that intends to measure boredom. For example, it is possible to develop a four-point scale and have individuals rate their boredom on it. But what does a score of “4” mean on such a scale? We can assign a number but it doesn’t carry any meaning.

Qualitative assessments assume that each individual has a different experience and that it is important to provide the opportunity to capture that experience. There is no attempt to measure a particular construct. Rather, the purpose is to describe and understand the user’s experience with the technology. Qualitative assessments may include observation, either directly or via videotape, or interviews with the client and others. Qualitative assessments often capture those experiences which cannot be directly quantified or for which quantification holds little meaning. They provide the client with the opportunity to identify issues, experiences, or goals that may not have been previously identified on a quantitative measure.

Both qualitative and quantitative assessment formats are important in the AT assessment process and for evaluation of the outcomes of AT use. Quantitative measures allow comparison of experiences of a large number of individuals, and a well-constructed instrument is essential in building evidence to support the efficacy of AT use. Qualitative methods provide a rich description of AT user experiences that may not be readily apparent from the use of quantitative instruments alone. Together these methods can provide strong support for AT use, both on an individual and collective basis.

Norm-Referenced and Criterion-Referenced Measurements

Two commonly used standards are employed for measuring performance (for both the human and the total system): norm referenced and criterion referenced. In norm-referenced measurements the performance of the individual or system is ranked according to a sample of scores others have achieved on the task. Norm-referenced measures usually produce a percentile rank, a standardized score, or a grade equivalent that indicates where the individual stands relative to others in the representative sample.⁴⁹ It is important to review how the norms were developed when selecting a norm-referenced test for use. Norms need to be relevant to the population with which the instrument is being used. They need to be recent and representative.⁴⁸ In other words, the characteristics of the sample used to develop the norms must be similar to those of the client group with which the assessment is being used. The items that form the instrument need to be relevant to the client group. For example, assessing visual-perceptual skills using blocks is not relevant for most adults. Similarly, the use of outdated questions or materials will not give an accurate picture of the client’s abilities. For example, testing keyboarding skills on a typewriter will give some information on keyboarding skills but does not cover the full range of skills required to use a computer.³² An alternative way to assess human or system performance is to rate the performance according to a specified criterion or level of mastery, which is referred to as criterion-referenced measurement, and the person’s own skill level in using the system is used as the standard. Criterion-referenced measurement requires that different degrees of competence in the functional ability to be measured can be expressed. One standardized method of achieving this description is through Goal Attainment Scaling (GAS).²¹ This method involves a consensus-driven process where a target behavior is identified and five levels of competence are clearly articulated. These are coded on a 5-point scale from − 2 to + 2. The zero point on the scale represents basic or minimum competence. The points below zero represent inadequate performance and those above zero are better than expected performance. Goals are specific, measureable, and time specific. Benefits to using GAS are that it is flexible, identifies performance over time, and is individualized to the client. However, it is time consuming and, because it is individualized, may not easily capture a range of functional activities. An example of GAS goals is shown in Box 3-2.

Box 3-2 An Example of Goal Attainment Scaling Goals

Target Behaviour: Client will be able to self-initiate a wheelie with their manual wheelchair and hold the position momentarily.

+ 2: Client is able to self-initiate a wheelie with their manual wheelchair and propel the chair forward for a short duration. [Client achieves target behavior and demonstrates a high level of competence.]

+ 1: Client is able to self-initiate a wheelie with their manual wheelchair and hold the position for one minute. [Client achieves the target behaviour and demonstrates a moderate level of competence.]

0: Client is able to self-initiate a wheelie with their manual wheelchair and hold the position momentarily. [Client achieves target behavior.]

– 1: Client is able to hold a balanced wheelie position for one minute if another person assists her to assume the wheelie position [Client does not achieve the target behavior but is successful with a somewhat less difficult skill.]

– 2: Client is unable to hold a balanced wheelie position when another person assists her to assume the wheelie position. [Client is unable to self-initiate the wheelie position. This level is often the client’s starting skill level.]

When we use the criterion-referenced approach to measurement, we accomplish two desirable goals. First, we base our assessment of progress on the person’s unique set of skills and do not attempt to relate this performance to a normalized standard. The second goal we accomplish by using the person’s own performance as a standard is that we have a way of measuring progress.

Needs Identification

Through the needs identification process we determine the individual’s needs and goals, which provide the basis for the assistive technology intervention. Identifying the needs of the consumer is the most critical component of the service delivery process and must be completed at the onset of evaluation. The information collected during needs identification is the cornerstone for measuring the effectiveness of the final outcome. Therefore it is important to take this step seriously and ensure that there is a consensus among those involved both as to the nature and scope of the problem to be addressed by the assistive technology intervention and the goals identified to target these problem areas.

Information gathered during needs identification is also used by the ATP to justify purchase of services and equipment. Third-party payers who fund services and equipment want to know what the problem or need is and how the equipment is going to address the need. Finally, the needs identification process results in the development of a plan for completing the remainder of the evaluation, which includes composition of the evaluation team, determination of needed evaluation tools and devices, and identification of further information required (either through evaluation of the consumer or by request from outside sources).

The purpose of the initial interview is to establish the needs and goals of assistive technology intervention. In this interview the consumer and/or caregivers frame the performance issue that brings them to the assistive technology service. The ATP guides this interview to determine the activities of self-care, work, and leisure in which the client wishes to engage and identify those aspects of performance for which assistive technology has potential benefit. Information is secured about the consumer’s medical information, daily activities, settings in which these activities occur, and current or past experience with assistive technology. Information is also gathered about current or potential sources of funding. Depending on the service delivery model, a more in-depth assessment will be conducted during the same session as this initial interview. In other models, this initial interview serves to determine the appropriateness of the referral and then funding is required to proceed with further stages of the intervention process. The components of an in-depth assessment will be described in the following sections.

The information for the needs assessment can be derived from an interview or through a written questionnaire completed by the consumer or his representative. Instruments such as the Matching Person and Technology Assessment ⁴² can also be used by the ATP to identify the areas of the individual’s needs and his predisposition to use assistive technology. If the information is gathered through a written questionnaire before actually meeting the consumer, it should be reviewed at the time of the first meeting with the consumer. The purpose of reviewing this material at the first meeting is to ensure that all the necessary information has been provided and to analyze the information to develop the goals. In addition, the provider needs to ascertain that the consumer understands the questions that were asked. The total team should also be present at this meeting, and everyone’s input regarding the needs and goals of the consumer can be discussed and a consensus reached.

Once the client has clarified their activity needs, a more detailed evaluation of specific components follows. This evaluation includes assessment of basic skills, including sensory, physical, cognitive, affective (emotional), and communication skills; performance in functional activities; and relevant aspects of the context in which the client engages in activities. Some of the evaluation data are gathered from reports of other professionals, such as assessment of visual function by an optometrist or ophthalmologist. Other data are gathered by a collaborative effort of the team, including the rehabilitation assistant. The integration of all of the evaluation information is important for the rehabilitation assistant to understand because it influences her involvement in the implementation and follow-up stages.

Skills Evaluation: Sensory

The rehabilitation assistant needs to understand the sensory functions that are available to the client when using assistive technologies. If the primary disability is sensory, an alternative sensory pathway may need to be used and we need to know what the consumer’s sensory capabilities are. For example, in the case of a consumer who is blind and who needs to read, the ATP must evaluate tactile and auditory skills that can substitute for vision during reading.

In other cases a consumer may have a sensory disability secondary to either a physical or cognitive limitation. For example, if a consumer is hard of hearing, the ATP needs to know how this will affect interaction with technology, including everything from hearing warning beeps when a computer error is made to understanding voice synthesis on a communication device. The chapters that describe assistive technology for specific activity outputs discuss the implications of sensory limitations to the use of the technology and how modifications can be made to accommodate for these limitations.

Evaluation of Functional Vision

The most critical visual skills needed for assistive technology use are sufficient acuity to see the symbols used in the system of choice, or to identify small objects in the environment; adequate visual field to allow receipt of information from a display (e.g., the keyboard or the monitor) or the environment; and sufficient visual tracking ability (e.g., for reading or tracking a moving cursor). Known visual problems should have been identified during the initial interview. A visual evaluation by a vision care professional will provide information about the following visual functions.

A visual field deficit can be experienced in two ways: loss of peripheral vision or loss of central vision (Figure 3-2). Peripheral vision loss results in a narrowing of the visual field, commonly an age-related deficit.^38,⁴¹ This type of loss makes it increasingly difficult to see objects to the side, potentially causing difficulties when maneuvering a wheelchair through a crowded environment. A central field loss has more significant functional implications because the individual loses the ability to see something they are looking at directly. Age-related macular degeneration and diabetic retinopathy are two common central field deficit disorders.

Figure 3-2 Types of visual field deficits. A, Retinal lesion: blind spot in the affected eye. B, Optic nerve lesion: partial or complete blindness in that eye. C, Optic tract or lateral geniculate lesion: blindness in the opposite half of both visual fields. D, Temporal lobe lesion: blindness in the upper quadrants of both visual fields on the side opposite the lesion. E, Parietal lobe lesion: contralateral blindness in the corresponding lower quadrants of both eyes. F, Occipital lobe lesion: contralateral blindness in the corresponding half of each visual field, but with macular sparing. (From Umphred DA, Burton GU, Lazaro RT, Roller ML, eds: *Neurological Rehabilitation*, ed 5, St. Louis, 2007, Mosby, page 977. Courtesy Smith Kline & French Laboratories, Philadelphia.)

Visual acuity refers to the clarity with which a person can see objects in the environment.³⁸ The loss of this visual function is probably the best understood as it occurs so frequently in the population. There are three types: myopia (near-sightedness); far-sightedness; and presbyopia (the inability to focus on a near object), which is an age-related visual change. All of these functions result from an inability to focus the image on the retina. In most cases, functional vision is restored with the use of corrective lenses (glasses or contact lenses) or laser surgery. Chapter 8 discusses assistive technology to assist individuals with low vision or blindness, for whom these common interventions are inadequate.

Visual tracking refers to the ability to track a moving object with the eyes; for example, tracking the movement of a cursor on a computer screen.^15,³⁸ Evaluation of visual tracking includes the coordination of both eyes, tracking ability in vertical and horizontal planes, smoothness of the movements, delay in the initiation of visual tracking, and the ability to track without moving the head. Visual scanning refers to the ability to scan the environment to gather visual information. In this situation, the object doesn’t move; instead, the eyes are moving.¹⁵ Visual scanning is most commonly used when reading text. Clients who have had a stroke may have a visual scanning impairment if they also have a neglect of one side of the body. In this situation, the eyes do not move past midline, so visual information on the affected side of the body is not detected.

Visual contrast is required to differentiate a figure from its background, and is commonly used during reading and in retrieval of information from a display.⁴¹ With age and other visual impairments, contrast needs to be enhanced in order for the user to detect the information. Visual accommodation is the ability of the eyes to re-focus when shifting attention between different locations³⁸; for example, shifting attention from the board to a notebook when taking notes during class or shifting attention from the road to displays on the vehicle instrument panel while driving. This function requires coordination of the small muscles of the eye.

Evaluation of Visual Perception

Visual perception is the process of giving meaning to visual information. Visual perceptual skills that need to be considered during the AT assessment include depth perception, spatial relationships, form recognition or constancy, and figure-ground discrimination. Visual perception is an important consideration when considering the client’s ability to interpret information presented in a visual display or to safely navigate a mobility device in their environment. Formal testing of the consumer’s visual perception may have been completed before the assistive technology assessment, and the results of this evaluation can be reviewed during the initial interview. The rehabilitation assistant may have completed parts of the visual perception assessment. It is necessary to observe the consumer during functional tasks and note any apparent perceptual problems. If there is still some concern regarding the exact nature of the problems, a formal evaluation such as the Motor-Free Visual Perception Test can be used.⁷

Figure-ground perception refers to the ability to discriminate between an object in the foreground and the background on which it rests. For example, recognizing that a white sock is different from the white sheet on which it rests is an indicator of intact figure-ground perception. Vision is certainly a key element of this skill, but other aspects such as recognition of the object and form constancy affect the ability to differentiate an object from the background. Figure-ground perception is also an element of hearing, and refers to the ability to discriminate a sound from background or ambient noise.

Spatial relations involve understanding basic concepts such as up/down and right/left as well as understanding the relationship of objects to each other (e.g., on top of, or in front of, another object). This perceptual function is key to safe movement in the environment.

Form constancy or recognition involves the understanding that an object does not change, despite being viewed from different perspectives, either as the object itself is moved or as the person moves around the object. For example, intact form constancy allows a person to recognize the size and shape of objects in the environment as well as to recognize that an object hasn’t changed, despite viewing it from various perspectives.

Evaluation of Auditory Function

Formal evaluation of auditory function is conducted by an audiologist. Any significant auditory impairment that has been previously diagnosed should be identified in the initial referral or during the needs assessment. In cases of suspected hearing loss, referral should be made to an audiologist. She will determine auditory thresholds, including frequency and amplitude. The amplitude of sound is measured in decibels (dB). This minimum threshold is equivalent to the ticking of a watch under quiet conditions at a distance of 20 feet.

The typical range of frequencies that can be heard by the human ear is 20 to 20,000 hertz (Hz).² However, the ear does not respond equally to all frequencies in this range. A combination of frequency and amplitude determine the auditory threshold. Pure tone audiometry presents pure (one frequency) tones to each individual to determine the threshold of hearing for that person. The intensity of the tone is raised in 5-dB increments until the stimulus is heard. It is then lowered in 5-dB decrements until it is no longer heard. The auditory threshold is the intensity at which the person indicates that she hears the tone 50% of the time.³

Only gold members can continue reading. Log In or Register to continue