Persons who are deaf-blind represent a heterogeneous, low-incidence population of children and adults who, at some point in life, regardless of the presence of additional disabilities, may benefit from formal orientation and mobility (O&M) instruction. Huebner, Prickett, Welch, and Joffee (1994) emphasized the importance of children who are congenitally or adventitiously deaf-blind receiving systematic instruction to learn to be oriented and independent across multiple environments. Bourquin and Sauerburger (2005) stressed the need for training in "real-world" environments that can empower adults who are deaf-blind to overcome everyday hurdles in accessing their communities. Current national policies, such as the No Child Left Behind Act, which emphasize that instructional practices must be validated through the use of scientific measurement using randomized clinical trials, present specific problems for O&M professionals who serve students who are deaf-blind. Heterogeneity within the population, diversity of settings, geographic spread, cost, random sampling, and ethical concerns present immediate challenges in conducting experimental group designs with persons who are deaf-blind (Parker, Davidson, & Banda, 2007). Specifically in the area of O&M research, Long (1990) enumerated the challenges in conducting truly experimental research because of the need to account for environmental, instructional, and student-specific variables within a variety of travel contexts.
The Council for Exceptional Children's Division of Research and the National Center for Special Education Research have recognized that the alignment and systematic analysis of single-subject research can be used to evaluate the efficacy of practice (Homer, Carr, Halle, Odom, & Wolery, 2005). In his review of O&M research, Long (1990) recommended single-subject designs for establishing the field's knowledge for serving persons who are deaf-blind. Furthermore, this type of research allows for the tailoring of intervention strategies to meet the unique needs of participants and may be implemented in an experimental fashion without relying on traditional parametric analysis (Tawney & Gast, 1984). In the field of visual impairments, single-subject research has been used to measure the impact of teaching over the years (LaGrow & Murray, 1992). Parker et al. (2007) began an initial examination of single-subject methodology with participants who had dual sensory impairments; however, at this point, there has been no comprehensive review of single-subject research with participants who are deaf-blind specifically in O&M interventions. The study presented here sought to answer the following research questions: (1) What types of single-subject research were conducted with participants who are deaf-blind from 1965 to 2007 in the area of increasing O&M skills? and (2) What types of interventions and practices were shown to be effective in building participants' competence in the areas of O&M?
Studies were culled through the following databases: DB-LINK (the National Information Clearinghouse on Children and Youth Who Are Deaf-Blind), Google Scholar, PsycINFO, ERIC, and Academic Search Premier. Search terms included deaf-blind studies, orientation and mobility, dual-sensory impairment, single-subject designs, single-case research, intervention, and research in deaf-blindness. To be considered for evaluation, the studies had to be published in peer-reviewed journals, to include at least one or more deaf-blind persons as participants, to focus on some type of intervention or teaching practice that related to building the person's orientation or mobility skills, and to use single-subject design methodology and not some other type of research design.
Of the 860 articles I reviewed, I identified 13 studies, published from 1988 to 2007, that met the search requirements. It was striking that all the research within this initial search was conducted by the same lead scholar. …