Failure to detect deaf-blindness in a population of people with intellectual disability

Early identification of deaf-blindness is essential to ensure appropriate management. Previous studies indicate that deaf-blindness is often missed. We aim to discover the extent to which deaf-blindness in people with intellectual disability (ID) is undiagnosed.

A survey was made of the 253 residents of an institute offering residential and occupational facilities for people with IDs. Data are included for the 224 individuals who were able to complete both auditory and visual assessments. Otoacoustic emissions were used to screen for hearing impairment; those who did not pass were assessed by behavioural audiometry. Visual acuity was assessed with one of the following: EH-Optotypes, LH-Optotypes, Teller Acuity Cards, Cardiff Acuity Cards or the Stycar Ball Vision Test.

Prior to the study hearing impairment had been diagnosed in 12.5% of the 224 subjects, and visual impairment in 17%. Upon completion of the study these figures rose to 46% and 38.4% respectively. Deaf-blindness was diagnosed in 3.6% of the subjects before, and in 21.4% after, the study. Most (87.5%) of the deaf-blind individuals had profound ID.

Deaf-blindness is most often not identified either by standard medical screening or by care staff. Individuals with this disability, however, require provision of special kinds of care. Four categories of deaf-blindness are proposed, according to the severity of sensory impairment in each modality. The tests used in this study are non-invasive and are appropriate for individuals with ID and children. Early and periodic screening for visual and hearing impairment in individuals with ID is recommended.