With aging comes change in both the auditory and visual systems. Some changes such as presbycusis and presbyopia are a result of normal aging; others, such as noise-induced hearing loss and ototoxic damage due to medications, are secondary to accumulated environmental exposures. Visual changes may be associated with age-related pathologies such as macular degeneration, cataract, glaucoma, and diabetic retinopathy. Regardless of etiology, these changes result in degrees of concomitant hearing and vision loss, and are referred to as dual sensory impairment (DSI).

Studies show that between 9% and 22% of adults older than 70 years have some degree of DSI, and that its prevalence increases with age (Campbell et al., 1999; Lighthouse International, 2002; Jee et al., 2005). Relative to those with single or no sensory impairment, individuals with DSI have poorer self-rated health, are more likely to be depressed, experience greater cognitive and functional decline, and participate in fewer social activities (Capella-McDonnall, 2005; Crews & Campbell, 2004; Chia et al., 2006). Studies show that although intact hearing and vision are both required for optimal functioning, vision is most necessary for interaction with the physical and spatial world, and hearing is most necessary for the social world (Wahl & Tesch-Romer, 2001). It is commonly postulated that the effect of DSI on function and quality of life is greater than the sum of the effects of the individual sensory impairments because the individual with DSI cannot compensate for a single sensory impairment with the second sense. To date, however, this hypothesis has not been examined in a rigorous study (for a review, see Saunders & Echt, 2007). 

Assessment and Treatment 

In current clinical practice, hearing and vision are assessed and treated in isolation using sense-specific measures to document either hearing impairment or vision impairment. Auditory impairment is documented based on unaided ability to hear; visual impairment is classified using best-corrected vision. Auditory impairments are defined based primarily on threshold testing; definitions of visual impairment center on the ability to resolve high-contrast spatial detail (acuity) and on visual fields. There is no unified classification system for DSI, which is unfortunate because such a system could assist clinicians in making evidence-based decisions regarding optimal interventions for someone with, for example, a mild hearing impairment coupled with severe vision impairment, versus someone with moderate hearing and visual impairments.

The effect of DSI on function is similarly assessed independently. For example, there are measures of the extent to which a hearing impairment limits speech understanding in a noisy place, or to which a vision impairment limits ability to read under less-optimal lighting conditions, but no measures assess the combined impact of poor vision and hearing on ability to function in the real world. Given that uptake of information from our surroundings is usually from both senses (sensory integration), there is a need to develop measures that are equally sensitive to auditory and visual (dys)function. Only through such tools will we be able to understand the true impacts of dual sensory loss.

Assistive technologies and rehabilitation practices also have been developed in isolation, with little regard for usability by individuals with DSI. For instance, most hearing aids have components that are difficult to see and handle; written instructional materials are provided to assist with their use; and listening tips often focus on using visual cues to supplement the limitations from missing auditory input. Likewise, vision rehabilitation professionals provide patients with assistive technologies that provide auditory signals to compensate for vision loss, such as audible prescription-label readers, screen readers, and spoken books. It would seem that technology could be developed that can enhance both the visual and auditory signals simultaneously or that provides complementary tactile information to supplement limited auditory and visual function. Such approaches would potentially enhance multisensory integration processes.

Age-related DSI arises in the context of numerous other age-related changes, such as diminished cognitive capacity, decreased manual dexterity, and changes in communication needs and lifestyle (Salthouse, 2004; Carmeli et al., 2001; Meister et al., 2002). These issues must be considered when developing rehabilitation strategies (Saunders & Echt, 2007). The goal of cross-disciplinary rehabilitation is to address DSI within the context of the whole individual, taking into account the DSI as well as other co-impairments, with the goal of restoring full participation in society and ensuring individuals have the full capacity to participate in education, vocation, independent living, social activities, relationships, and recreation. To this end, strategies should be developed to optimize residual capacities, accommodate losses, and teach compensatory strategies; these strategies will require tailoring environmental, technologic, and training/re-training rehabilitative interventions to maximize functional independence.

Innovative and integrative approaches to assessment and care are needed and should involve interdisciplinary education of audiology and vision providers and multisensory team-based models of care, as well as interdisciplinary industrial partnerships between hearing and vision device manufacturers for improved product design.