This chapter provides an overall introduction to observation of vision, hearing and the bodily-tactile sense as a basis for the functional assessment of deafblindness. The aim is to direct attention to how the senses are used in everyday life, particularly in work with the indicators for observation.
Observation of sensory use may be demanding, as persons with suspected deafblindness often have complex disabilities. Observations in natural situations, possibly supplemented by interview, provide important information about how residual senses are used and compensate for one another.
3.1 Vision
Vision provides rapid and extensive information about the environment and is of great importance for communication, acquisition of information, orientation and independent mobility (Befring & Tangen, 2012). For persons with deafblindness, it is especially important to understand how any residual vision is used functionally in interaction with other senses.
Even small amounts of residual vision may be of great value for independence, communication and orientation, for example in perceiving light, contrasts or contours. At the same time, reduced vision may be energy-intensive to use and requires environmental adaptations. In functional deafblindness, hearing cannot fully compensate for visual impairment, which may lead to fragmented sensory impressions.
In assessment, it is therefore important to identify how vision is actually used in practice, also when both vision and hearing are reduced, and how the environment can best support the functional use of any residual vision.
3.2 Hearing
Hearing contributes to communication, orientation and understanding of the environment and may provide meaning and recognisability even when reduced. For persons with deafblindness, auditory functioning varies considerably, from total deafness to useful residual hearing (Mjønes, 2019).
When vision is also impaired, it becomes more difficult to interpret and locate sounds. Listening may then be demanding. Functional use of hearing is not static but may change over time and in different situations.
In the assessment of deafblindness, it is therefore important to focus on how hearing and listening skills are used in practice and what support is necessary to promote the functional use of residual hearing.
3.3 Bodily-tactile sense
When vision and hearing are so reduced that they cannot compensate for one another, the bodily-tactile sense assumes a central role in communication and interaction, acquisition of information, and orientation (Nordens Velferdssenter, 2016; Andersen & Rødbroe, 2000).
The bodily-tactile sensory apparatus includes the processing of touch, pressure, vibration, temperature, pain and proprioception through the somatosensory system (Nicholas, 2021; Gallace & Spence, 2009). Through active touch and movement, bodily-tactile and haptic perception may provide structured and meaningful information about the environment (Nicholas, Johannessen, & van Nunen, 2019; Prytherch & McLundie, 2002).
For many persons with congenital deafblindness, the bodily-tactile sense is the most stable modality for learning, security and communication (Wittich, Nicholas, & Damen, 2021; Ravenscroft & Damen, 2019). Effective use of this sense presupposes physical proximity, adapted surroundings and competent communication partners. In assessment, it is therefore crucial to describe how the bodily-tactile sense is used functionally to compensate for visual and hearing loss.