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Deafblindness

Condition of little or no useful sight and little or no useful hearing

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Through Communication, Braille and Language interpretation

People with deafblindness form a highly heterogeneous population. Individuals may have different degrees and types of residual hearing and vision, and deafblindness may be congenital, acquired during childhood or adulthood, progressive, or associated with ageing. Few people with deafblindness are both completely deaf and completely blind.

The effects of deafblindness depend not only on the degree of sensory impairment but also on factors including the age and sequence of onset, communication and language development, associated health conditions, environmental accessibility and the availability of support. Commonly affected areas include communication, access to information, orientation, mobility, social interaction and participation in everyday life.

Communication methods vary according to an individual's sensory abilities, previous language experience and preferences, and may include spoken language, adapted visual or tactile signing, fingerspelling, Braille, assistive listening and visual technologies, or combinations of these methods. The tactile sense can become particularly important where vision and hearing cannot adequately compensate for one another.

Estimates of prevalence vary substantially because studies use different definitions, sensory thresholds and age groups. Deafblindness and the broader concept of combined or dual sensory impairment become increasingly common with age.

Definition and terminology

There is no single universally applied clinical or epidemiological definition of deafblindness. Definitions vary between countries, service systems and research studies, particularly in the degree of hearing and vision impairment required and in whether classification is based on sensory measurements or on their functional consequences.

A widely used functional definition is the Nordic definition of deafblindness. In its 2024 revision, deafblindness is defined as a combined vision and hearing impairment of such severity that the two impaired senses have difficulty compensating for one another. It is consequently regarded as a distinct disability rather than simply the addition of separate hearing and visual impairments. This definition is also used by the World Federation of the Deafblind.

Under a functional approach, the consequences of deafblindness depend not only on the measured severity of each sensory impairment but also on factors such as the age and sequence of onset, whether the impairments are congenital or acquired, communication and language development, additional disabilities or health conditions, and the physical and social environment. The combined impairment may affect communication, access to information, orientation, mobility, social interaction and participation. People classified as deafblind therefore include individuals with substantial residual hearing or vision as well as those who are completely deaf and blind.

The terms dual sensory impairment (DSI), dual sensory loss (DSL), combined vision and hearing impairment and related expressions are also used in the scientific literature. Their use is inconsistent. In some studies they are used interchangeably with deafblindness, whereas in others they refer more broadly to the coexistence of any specified degree of hearing and visual impairment, irrespective of whether the combination produces the functional consequences associated with deafblindness. This variation in terminology and diagnostic thresholds complicates comparisons of prevalence and outcomes between studies.

Deafblindness is commonly described according to its timing and pattern of onset. Congenital deafblindness generally refers to combined hearing and vision impairment that is present from birth or develops before the acquisition of language and communication, whereas acquired deafblindness develops after communication or language has been established. Acquired deafblindness may result from a progressive disorder, from the later development of a second sensory impairment in a person who already has hearing or vision loss, or from sensory impairment associated with ageing. These categories are useful descriptively, but the boundary between congenital and acquired deafblindness is not defined uniformly across studies.

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