Abstract
This issue of Trends in Amplification is devoted to the topic of dual sensory loss, primarily in older adults, and represents proceedings from the State of the Science Conference on Hearing Enhancement held at Gallaudet University, Washington, DC, on September 18–20, 2006. The conference was organized by the Rehabilitation Engineering Research Center on Hearing Enhancement with funding from the National Institute on Disability Research and Rehabilitation. The third day of this conference focused exclusively on dual sensory loss and brought together experts from the fields of vision and hearing research and rehabilitation. In some cases, the presentations were collaborative, which served to extend our thinking in this area, offering a unique perspective on dual sensory loss beyond that offered by either discipline alone. In addition to identifying research needs, the speakers offered some practical considerations that can readily be adopted into current practice.
As the population ages, we will encounter an increasingly greater number of clients who have a combination of vision and hearing loss. These individuals present a complex and unique challenge to us professionally in terms of assessment and rehabilitation. The articles in this issue offer preliminary insights from experts in the fields of vision and hearing research and rehabilitation into understanding the effect of dual sensory loss, suggested approaches for assessment, and considerations for amplification and other assistive technology. They identify directions for future research and innovative approaches for intervention, laying the groundwork to help guide our clinical practice with this population.
The issue begins with an article by John Brabyn, director of the Rehabilitation Engineering Center on Low Vision and Blindness Research at the Smith-Kettlewell Eye Research Institute, and colleagues. The article provides an overview on vision loss and introduces us to the range of combined vision and hearing problems, from subgroups that have no residual hearing or vision to those that have acquired a mild loss of both vision and hearing later in life. It gives a framework for understanding the most common vision problems affecting older adults, how they are managed, and how visual impairment might affect receptive communication. It provides the audiologist with useful information about vision loss, implications for rehabilitation, and possible strategies to consider when working with individuals with age-related dual sensory loss.
The article by Hyvärinen that follows introduces us to the world of visual assessment with the deaf-blind population. In addition to a description of the protocols used for testing visual function, we learn about the special auditory needs of blind or visually impaired individuals with regard to spatial orientation and mobility issues. From this article, we also gain a better understanding of the communication problems we are likely to encounter during audiological assessment of a deafblind client, how to determine the appropriate distance and lighting needed to maximize the client's ability to speechread or view sign language depending on his or her visual disorder, and the role of interpreters in mediating this process for evaluation and intervention.
The next article by Tye-Murray et al considers audiovisual speech perception and how it may be affected by hearing or vision impairments. Using the theoretical approach involving lexical neighborhoods, the authors posit that audiovisual speech perception may be related to the density of the auditory and visual neighborhoods in which the word is found. Furthermore, the activation of these neighborhoods, and particularly the interaction of these modalities, may be responsible for why audiovisual speech performance is often greater when combined than would be predicted by auditory or visual performance alone. The integrity of these neighborhoods and of multisensory integration, particularly in the presence of dual sensory impairment, may have a notable effect on audiovisual integration and speech recognition. Possible implications for an older population with dual sensory loss are discussed.
Saunders and Echt provide an overview of the literature in the area of dual sensory loss from an audiological perspective. The authors describe the state of the research on dual sensory loss, including the nature of the populations that have been studied, the methods for delineating impairment (eg, measured or based on self-report), and the effect of dual sensory impairment on aspects of function and quality of life. The complexity of developing rehabilitative strategies with this population is described, noting the challenge that audiologists face when the dominant residual sense (ie, vision) cannot be relied on as a means of compensating for the existing hearing loss. In addition to the critical need for further research on dual sensory loss to inform clinical practice in this area, the authors call for interdisciplinary training of hearing and vision professionals to meet the special rehabilitation needs of this population.
The article by Simon and Levitt addresses key audiological issues related to dual sensory loss, with implications for amplification. The authors provide interesting insights into the role of plasticity and adaptation, as well as the capacity of one modality to supplement the function of the other. An underlying premise is that the amplification needs for individuals with dual sensory loss differ from those with only hearing loss. The authors maintain that sound localization and binaural processing are of major importance for speech perception and spatial orienting cues in individuals with both vision and hearing loss. Factors such as interaural time and intensity cues, which are important for sound localization, affect decisions regarding choice of signal processing. Furthermore, the balance between optimizing audibility and the role of directional compared with omnidirectional microphone arrays with this population is discussed.
The article by Kricos that follows considers the unique audiological rehabilitation needs of individuals with dual sensory loss, with an emphasis on hearing aids and other assistive technology. The importance of hearing assistive technology not only for communication but also for independence, mobility, and quality of life is emphasized. The article provides comprehensive treatment of issues central to clinical decision making with adults with combined vision and hearing loss. In essence, the author walks us through the entire fitting process with hearing technology, from candidacy issues to fitting, along with clinical recommendations for follow-up and support. Many practical considerations are offered, ranging from comparison of manual versus automatically changing directional microphones on hearing aids, the role of assistive technology, the types of visual devices to incorporate into a clinical practice, as well as what to consider when developing written materials that afford accessibility to adults with both vision and hearing loss.
Brennan and Bally author the final article in this issue, which addresses the psychosocial effect of combined hearing and vision loss in older adults. They begin by reviewing what is known in the separate disciplines and consider whether there is an additive or interactive aspect to dual sensory loss. Their article focuses primarily on coping and adaptation in older adults with dual sensory loss and does so through a framework of a unique model (ie, biopsychosocial model) in which a myriad of factors affecting psychosocial adaptation are examined. Strategies for coping and recommendations for rehabilitation are offered. Brennan and Bally provide an interesting new perspective on approaches to intervention that cross disciplines and potentially may improve not only function but also the independence and well-being of an individual with dual sensory loss.
The compilation of articles in this special issue contributes to our understanding of dual sensory loss and may help guide clinical management in this complex and challenging area. Experts from both fields suggest that current practices be replaced with a collaborative interdisciplinary model to better meet the needs of individuals with combined hearing and vision loss in later life. While this is an emerging issue in clinical practice, the authors in this journal issue have taken substantial steps toward identifying key assessment methods, along with approaches to rehabilitation and avenues for future research that may improve the quality of life for persons with dual sensory loss.