Deafblindness: dual sensory loss

What is dual sensory loss (deafblindness)?

This is a combination of deafness/hearing impairment and blindness/vision impairment. The hearing loss is 35 dB or more, visual acuity is 0.30 or less and/or the field of vision is 30˚ or less (see also 'impaired hearing' and 'impaired vision').

It is possible to distinguish between the following three forms of deafblindness:

1. congenital deafblindness, for example due to congenital rubella syndrome or CHARGE syndrome ⁵¹²
   
2. early acquired deafblindness, for example due to the Usher syndrome ⁵¹³
   
3. deafblindness in old age due to the combination of impaired vision and hearing attributable to old age; this may also be seen in people with Down syndrome ⁵¹²
   

What are the complaints associated with dual sensory loss (deafblindness)?

Deafblindness makes communication, the acquisition of information and mobility difficult. Without adjustments, aids and/or support, deafblind people cannot take part in a natural way in everyday and social life. The restrictions resulting from deafblindness are not the sum of the restrictions caused by deafness and blindness. There are new or more severe restrictions. This is often described as 1+1 ≠ 2 or 1+1 = > 2. For example, deaf people communicate using sign language and therefore compensate for their deafness by using their eyes. Blind people compensate by using hearing.

Compensation is difficult for deafblind people. And compensation is particularly difficult for people with intellectual disabilities. They find it difficult to imagine a space, to make an appraisal of a social situation, and to understand tactile information or information obtained from their limited hearing and vision. That exacerbates the challenges they face. All activities cost a lot of energy; fatigue is a common complaint. ²¹³

People with congenital deafblindness are more likely to have autism spectrum disorders than people without. Caution is advisable: the behaviour of people with congenital deafblindness resembles, in many ways, the behaviour of people with severe intellectual disabilities with an autism spectrum disorder. There is a risk of overestimating the role of an autism spectrum disorder and underestimating the role of deafblindness, and a corresponding risk of people with deafblindness not receiving the support they need to function optimally. ²¹⁴

A study of 95 people with congenital deafblindness found that 34% of them had an intellectual disability, and that 74% had a behavioural or psychiatric diagnosis. Specialised diagnostics and care are needed for these people to prevent the consequences of sensory deprivation being seen as behaviour problems or psychiatric diseases. ⁵¹⁴

How common is dual sensory loss (deafblindness) in the general population? ²¹⁵

It is estimated that deafblindness occurs in 0.01% of people under 50 years of age in the Netherlands. ²¹⁶

The prevalence of congenital deafblindness in Denmark has been calculated at 1:29,000 (0.035%). ²¹⁷

Of the people aged over 55 years in the Netherlands, 0.4% are deafblind, with the percentage for people in nursing homes being 12.7%. ²¹⁵

How common is dual sensory loss (deafblindness) in people with intellectual disabilities?

A major Dutch epidemiological study found dual sensory loss in 5% of 1598 adults with an intellectual disability. ²¹⁵  Broken down by age, the prevalence rate was found to be 2.9% in people <50 years and 11% in people > 50 years of age. Other risk factors were: severe intellectual disability and Down syndrome. The dual sensory loss was known to be present in only 12% prior to the study.

An Austrian study of 253 people with intellectual disabilities (of whom 79% had severe or very severe intellectual disabilities) found that 21.4% had dual sensory loss. People with intellectual disabilities and deafblindness are often not identified! ²¹⁸