2.5 Provide for users with multiple impairments
Users with multiple impairments, such as those who are both visually and hearing impaired, should still be able to use the application. Features that are provided to accommodate users with different impairments should therefore be supplementary rather than mutually exclusive. That is, using one should not prevent the user from using others. If possible, visually impaired users should be provided with facilities that do not require good hearing. And hearing impaired users should be provided with facilities that do not require good vision or reading ability.
Loss of vision, hearing and dexterity often occur together, particularly as the person gets older. For example, approximately 35% of people with a visual impairment also have a hearing impairment.
A high proportion of people who are deaf also have low literacy. A 1993 NRB survey found that 80% of deaf adults in Ireland had the reading age of an 8-9 year old. This is due to the difficulties of learning through sign language, which has a different grammar and structure to spoken or written language, or by lip reading.
Directions and Techniques
Make modes of use complementary
Where alternative or enhanced input and output modes are provided, such as large text, graphical buttons, large buttons and audio output, ensure that users can use them together. For example, instead of providing a choice between one user interface with large text and large buttons and another with spoken text and an spoken prompts, allow the user to choose any combination of these helpful features. The choice could be made by the user selecting from a number of displayed options.
How you could check for this:
There are no specific test methods recommended for this guideline.