By Griffin, Harold C.; Williams, Sarah C.; Davis, M. Lynne; Engleman, Melissa
Teaching Exceptional Children , Vol. 35, No. 2
Most people with visual impairments have some functional vision that they can use to facilitate their mobility and independent functioning. The term "low vision" (see box "What is Low Vision") was introduced after World War II, when a distinction from totally blind was necessary to tailor specific rehabilitation services for veterans returning to the work force (Goodrich & Bailey, 2000). In 1964, Barraga extended these distinctions to children when she investigated the learning characteristics of Children with visual impairments who had some functional vision. She showed that children with low vision could increase the efficiency with which they used their vision for visual discrimination (Barraga, 1964).
Since the 1960s, we have witnessed a tremendous growth in technology that can support and enhance low vision. In this article, we review some of the existing technology that assists children with low vision in their ability to use environmental cues.
Framework for Services
Recent research has emphasized that the education of children with low vision requires a transdisciplinary team effort (Wilkinson, Stewart, & Trantham, 2000). Such a team often includes the student, parents, technology consultant, orientation and mobility specialist, teacher of children with visual impairments, general education classroom teacher, and eye care professional. The team works together to provide services that will enhance the ability of children with low vision to utilize their residual vision.
Educators and researchers have proposed many models to guide decisions about service delivery and intervention plans. Colenbrander, Leigner, and Fletcher (1999) suggested that an effective model should consider lighting and contrast enhancement, as well as low-- vision aids for near and distance magnification. Corn (1983) originally proposed, and later revised (Corn 1989), a model that focuses on visual abilities, individuality, and environmental cues (see Figure 1). We use this model as a framework for discussing technology applications that enhance the use of residual vision and independence for students with low vision.
Corn's (1989) theoretical model for people with low vision consists of three interrelated components (see Figure 1), as follows:
* Visual Abilities consist of near-distance acuity, central and peripheral visual fields, and the mobility of the visual system. This component also addresses the functions of the brain that contribute to fixation, fusion, awareness of motion, changes in the lens, and light and color reception. Stored and Available Individuality includes cognition, sensory development and integration, perceptual abilities, psychological organization, and physical characteristics of the individual.
* Environmental Cues include color, contrast, and time elements involved in the presentation of materials; spatial relationships; and illumination.
Corn (1989) contended that the ability to use low vision is related to all factors in the model and that the interaction of these factors leads to greater visual efficiency in students with low vision.
Using Environmental Cues
We feel that the use of assistive technology is most applicable to the "environmental cues" component of Corn's model. The number and array of possible applications of assistive technology are too numerous for the scope of this article. Therefore, we discuss only a sample of representative applications. Table 1 provides additional examples and vendor contact information. As is illustrated in Figure 1, Corn's model of environmental cues stresses the elements of color, contrast, time, space, and illumination.
Color and Contrast
Corn's first environmental cue includes several aspects of color (Lang, 1993). These aspects are hue, lightness, and saturation.
* Hue is the attribute of color names (red, blue, yellow) and is ordered as they are produced in the light spectrum. …