AER Orientation and Mobility Division: Position Paper

AER Orientation and Mobility Division: Position Paper

Use of Visual Occlusion in Orientation and Mobility Instruction

Approved by O&M Division membership through mail ballot Spring 2004 (Approval percentage: 97%)

Revised 2013

Programs providing instruction in independent travel to individuals with functional/usable vision are most effective when they recognize the importance of using both visual and non-visual techniques to travel safely and efficiently. Although multiple references on low vision mobility exist, as early as 1982, Marron & Bailey (1982) recognized the fact that “any residual vision, even if it is only light perception, enhances orientation-mobility skills.” In 1989, this belief continued with Dodds and Davis reporting a new tool for evaluating the progress of individuals with low vision, that being the Percentage of Preferred Walking Speed (Dodds, Davis, 1989).It is clear in the literature throughout the yearsthat people travel differently depending upon the amount and type of vision that they possess (Morrissett, Marmor,Goodrich, 1983; Dodds, Carter, Howarth, 1983;Clark-Carter, Heyes, Howarth, 1986; Long, Rieser, Hill, 1990; Lovie-Kitchin, Mainstone, Robinson, Brown, 1990; Massof, Dagnelie, Benzschawel, Palmer, Finkelstein, 1990;Beggs, 1991; Smith, De l’Aune, Geruschat, 1992; Haymes, Guest, Heyes, Johnston, 1994; Haymes, Guest, Heyes, Johnston, 1996; Haymes, Guest, Heyes, Johnston, 1996; Kuyk, Elliott, Biehl, Fuhr, 1996;Geruschat, Smith, 1997; Geruschat, Turano, Stahl,1998;Ludt,Goodrich, 2002; Wall,Corn, 2006; Kuyk, Liu, Elliott, Fuhr, 2010; Cattaneo, Vecchi, 2011; Jacobson,2013).

Geruschat and Smith (2010),when considering the use of the blindfold as a training method, argue for a balanced approach. They state “The majority, if not all, of the training should emphasize the evaluation and use of existing vision and skills for determining when vision is or is not reliable for mobility judgments”.They further state that “it is important not to view blindfolding as an all or nothing prospect.” With the permission of the student, they recommend the judicious use of blindfolding to follow or interweave training in the combined use of vision and other sensory skills.
For some individuals, visual occlusion may be an effective method for teaching reliance on the use of other senses; trusting the use of the long cane, building confidence in handling dangerous mobility situations; and preparing for travel in varying lighting conditions. Best practice for individuals with low vision incorporates instruction in the use of remaining vision so that they will learn to use both visual and non-visual information simultaneously. While the use of visual occlusion is an appropriate instructional technique for many individuals, it must not be mandated as a condition for the receipt of instruction. The Rehabilitation Act through its various reauthorizations made it clear that consumer choice is a key ingredient in service provision. Therefore, when occlusion is to be used, it should be provided with the prior expressed consent of the individual receiving instruction. The professional orientation and mobility specialist, in consultation with the consumer and when appropriate the consumer’s family, should determine whether and how to make use of visual occlusion.
The Challenges of Travel with Partial Vision
There are four travel challenges for people with functional vision. They must learn:
1) non-visual techniques and how to trust the non-visual information;
2) how to use vision reliably and efficiently, while
3) not allowing vision to distract them from effective non-visual information; and
4) how to use non-visual and visual information together.
Consumers with visual impairment who have some degree of available functional vision benefit from learning to perceive and utilize information received by all their senses, including their vision, to travel safely and effectively. Those who have functional vision benefit from learning to use their vision effectively to gather information during travel.
In order to travel most efficiently, consumers with available functional vision need to perceive and utilize both visual and non-visual information simultaneously. Many consumers with low vision are unable to use visual and non-visual information together unless they receive instruction in how to integrate the use of both types of information as they travel. Therefore it is necessary to provide visual training along with non-visual strategies for travel.
Visual occlusion is one of several strategies available to teach consumers with functional vision to perceive and utilize non-visual information. For individuals who have unreliable vision or decreasing vision, the use of visual occlusion is often the best method of providing instruction. For others who have reliable vision that is stable, instruction while using both vision and non-visual strategies may be the best approach.
Teaching the Use of Vision
Consumers who have impaired vision do not automatically know how to use that vision efficiently. They must learn how much of their vision can be used reliably, and also learn the limits of their vision - that is, learn when they cannot rely on visual information, or when they can get the information much more effectively using non-visual techniques. Individuals with central scotomas need to learn how to use their best point of fixation for eccentric viewing. Individuals with peripheral visual loss need to learn to use scanning techniques effectively (Kuyk et al, 2010). In general, individuals with low vision need to learn to use their vision to identify the critical features in the environment that will provide the most information for travel (Ludt & Goodrich, 2002; Wall & Corn, 2006).
It is important for people to learn to travel with vision in real-life situations where conditions limit the amount they can see. Traveling in bright sunlight, in shaded areas, on overcast days, and at night will teach people how much they can rely on their vision and when they need to rely on one or more non-visual techniques in varying lighting conditions.
Individuals who can use optical devices to enhance their vision must also learn when and how to use those devices to their most effective end. This will include: positioning the device, viewing through the device, focusing, scanning, locating the target, and interpreting what is seen, as well as changing position when necessary for improved viewing (Wiener & Vopata, 1980; Jutai, Strong, & Russell-Minda, 2009).
The Use of Visual Occlusion
For some individuals the use of visual occlusion will serve as a helpful means of learning non-visual techniques because it prevents visual distractions and thus heightens awareness of the non-visual information that is present. With the vision occluded, the individual is able to concentrate on other sensory information. With experience, the traveler learns to use the remaining sensory information and to trust the information gained through the senses of audition, touch, proprioception, kinesthetic, olfactory and the vestibular sense.
When using visual occlusion for training, consumers are prevented from being distracted by vision but when vision is no longer occluded, many people will revert back to their old habits and let the vision interfere with their ability to notice and use the non-visual information. Thus, no visual occlusion program is complete unless the consumer learns to notice and use the non-visual information when the vision is no longer occluded.
If visual occlusion is considered for use with consumers who are Deaf or have a hearing impairment, it must be provided without compromising communication with the instructor. Instructional communication must be in the mode that is most effective to facilitate learning and put the consumer and instructor at ease during the instruction, and in many cases that means visual communication such as American Sign Language or speech reading (Bourquin, 1996, Sauerburger, 1993).
The Integration of Visual and Non-visual Techniques
Most often the issue is not simply whether to use or not to use visual occlusion. Rather, the issue is how to provide instruction in the use of visual and non-visual information so that both can be used simultaneously. Such integration of visual and non-visual information can be taught by using intermittent and/or partial occlusion.
With intermittent occlusion, the consumer may perform a task visually, and then repeat the task while the vision is occluded. The order of presentation may be varied but the intent is to allow the individual to compare the information available both with and without vision. This helps the individualunderstand the uses and limitations of vision. It prepares the person for use of vision and non-visual information in real life situations.
With partial occlusion, the bottom half of the consumer’s vision is covered so that he or she can’t see what is on the ground in front of the next step. The individual must rely completely on the non-visual information that the cane provides while, at the same time, looking ahead to gain clues about the surroundings. Partial occlusion has been shown to be effective in enabling people to notice and use their cane information at the same time that they notice and use visual information (Lauren, 1988).
When to Introduce Visual Occlusion
A final concern when considering the use of visual occlusion is the adjustment of the individual to his or her loss of vision. Instructors must be cognizant of the fact that although clinically the visual occlusion method may be beneficial to specific consumers, it is vitally important to take into consideration the emotional acceptance of the consumer for this teaching strategy prior to its use. According to Livneth’s Model of Adaptation to Disability (Livneth, 1999), there are five phases of adjustment: During “initial impact” and “defense mobilization” phases, the individual resists awareness of the disability. In the next three phases, “initial realization,” “retaliation,” and “reintegration,” the individual moves from realizing the disability to fully accepting the disability. The cognitive defenses and emotional components are distinctly different in each of the phases.
Introduction of visual occlusion before the individual is ready to accept the challenges of the disability can result in rejection of training or return to an earlier phase of adjustment. It therefore takes an instructor with a sensitive understanding of the individual’s adjustment to determine when
occlusion is appropriate.
Who Should Determine the Use of Occlusion?
As with any intervention technique used in education and therapy, the direct service provider is in the best position to consult with the consumer regarding potential service approaches and understand the consumer’s needs. In teaching orientation and mobility strategies, the O&M specialist is uniquely prepared to evaluate the consumer’s use of functional vision and work with the consumer to design an instructional program that is appropriate for that consumer’s needs. Together with the consumer, and where appropriate with the consumer’s family, the O&M specialist is the professional designated to determine when instruction in the use of available vision, occlusion of available vision, or a combination thereof, are effective strategies in the provision of orientation and mobility instruction.
References
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Bourquin, E. (1996). Using Interpreters with deaf‑blind clients: What service providers should know. RE:view, Winter 1996, pp. 149-153
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Clark-Carter D.D., Heyes A.D., and Howarth C.I. (1986). The efficiency and walking speed of visually impaired people. Ergonomics, 29(6):779-789.
Dodds, A, Davis, D. (1989). Assessment and Training of Low Vision Clients for Mobility, Journal of Visual Impairment and Blindness, November: pp 439-446)
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