Deafblindness is the combination of vision and hearing impairment to a degree that the impaired senses cannot fully compensate for one another. It is therefore regarded as a distinct disability rather than simply the coexistence of deafness and blindness.
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.
Causes and onset
Deafblindness has heterogeneous causes and may be present from birth, develop during childhood or adulthood, or arise later in life when hearing and vision impairments coexist. The relative importance of different causes varies substantially with age, population and the definition of deafblindness used.
Genetic and congenital causes
Genetic disorders are important causes of both congenital and progressive deafblindness. Usher syndrome combines sensorineural hearing loss with progressive retinitis pigmentosa and is one of the best-characterized inherited causes of deafblindness. Its clinical course varies according to genetic subtype; hearing loss may be congenital or progressive, while retinal degeneration usually develops later.
CHARGE syndrome, most often associated with pathogenic variants in CHD7, is an important cause of congenital deafblindness. Visual impairment commonly results from ocular coloboma, while hearing impairment may arise from abnormalities of the external, middle or inner ear and from cranial nerve dysfunction. Vestibular impairment and multiple additional medical and developmental conditions are also common.
Other genetic conditions can produce combined hearing and visual impairment through different mechanisms, including retinal dystrophy, optic neuropathy, structural ocular abnormalities or neurodegenerative disease. Examples include some forms of Alström syndrome, Wolfram syndrome, Stickler syndrome, mitochondrial disorders, peroxisomal disorders and other rare syndromic conditions.
Congenital deafblindness may also result from prenatal infections or developmental injury. Historically, congenital rubella syndrome was an important cause, producing combinations of sensorineural hearing loss, cataract or other ocular abnormalities and additional systemic manifestations. Congenital cytomegalovirus infection can also cause sensorineural hearing loss and visual impairment, particularly when central nervous system or ocular involvement is present. Other congenital infections may occasionally produce combined sensory impairment.
Prematurity and perinatal causes
Extreme premature birth can lead to combined visual and hearing impairment through several pathways. Visual loss may result from severe retinopathy of prematurity, cerebral visual impairment or other neurological injury, while hearing loss may be associated with extreme prematurity, neonatal intensive-care complications, ototoxic exposure, severe infection or neurological injury. Deafblindness in children born very preterm therefore often reflects multiple interacting causes rather than a single disorder.
Hypoxic-ischaemic brain injury, meningitis, encephalitis, severe neonatal infection and other neurological conditions can likewise affect both auditory and visual pathways. In some individuals the sensory impairment is partly peripheral and partly central.
Acquired and progressive causes
Deafblindness can develop when a person with an existing hearing or visual impairment later develops impairment of the other sense. Progressive genetic disorders such as Usher syndrome are a characteristic example, but combined sensory impairment may also follow trauma, infection, inflammatory or neurological disease, ototoxicity, retinal or optic nerve disease, or other acquired conditions.
In adulthood and particularly in older age groups, deafblindness frequently results from the coexistence of common acquired causes of hearing and vision loss rather than from a single syndrome. Age-related hearing loss may coexist with age-related macular degeneration, cataract, glaucoma, diabetic retinopathy or other ocular disease. Consequently, the etiological profile of late-life deafblindness differs substantially from that of congenital or early-onset deafblindness.
In some people no single cause can be identified, and more than one condition may contribute to the combined sensory impairment. Etiological classification therefore does not always correspond directly to functional severity or support needs.
Communication
Deafblind people communicate in many different ways as determined by the nature of their condition, the age of onset, and what resources are available to them. For example, someone who grew up deaf and experienced vision loss later in life is likely to use a sign language (in a visually modified or tactile form). Others who grew up blind and later became deaf are more likely to use a tactile mode of spoken/written language. Methods of communication include:
Use of residual hearing (speaking clearly, hearing aids, or cochlear implants) or sight (signing within a restricted visual field, writing with large print) Tactile signing, sign language, or a manual alphabet such as the American Manual Alphabet or Deaf-blind Alphabet (also known as "two-hand manual") with tactile or visual modifications Interpreting services (such as sign-language interpreters or communication aides) Communication devices such as Tellatouch or its computerized versions known as the TeleBraille and Screen Braille Communicator. Tadoma, a tactile modality Square script, a method of writing along tactile guidelines Protactile, a tactile language related to American Sign Language in the Francosign language family
Multisensory methods have been used to help deafblind people enhance their communication skills. These can be taught to very young children with developmental delays (to help with pre-intentional communication), young people with learning difficulties, and older people, including those with dementia. One such process is Tacpac.
Deafblind people often use the assistance of people known as support-service providers (SSPs), who help the deafblind with tasks such as routine errands, guiding the deafblind through unfamiliar environments, and facilitating communication between the deafblind person and another person.
Technology
Assistive technology can support communication, access to information, environmental awareness, orientation and mobility, and independent living for people with deafblindness. Because the degree and combination of hearing and vision impairment vary widely, technologies that are effective for people with only visual or only hearing impairment may be less usable when both senses are affected.
Access to information and communication
People with usable residual vision may use enlarged text, high-contrast interfaces, screen magnification or other visual adaptations, while those who primarily access information through touch may use refreshable Braille displays, Braille keyboards and other tactile interfaces. Screen readers can also be useful when sufficient hearing remains or when their output is routed to a Braille display. Smartphones, tablets and computers increasingly combine accessibility functions such as magnification, text-to-speech, Braille input and output, speech recognition and vibration-based notifications.
The suitability of a particular technology depends on sensory function, communication preferences, previous experience, cognitive and motor abilities, environmental conditions and the accessibility of the software or service being used. Assistive products for communication are among the environmental factors most frequently identified as relevant to functioning in research underlying the International Classification of Functioning, Disability and Health Core Sets for deafblindness.
Hearing and visual technologies