The intention with the Short Set questions is to record, with the exception of seeing and hearing, difficulties people have with unaccommodated functioning (without the use of assistive devices or assistance).
The WG wants to be able to identify difficulties in functioning that may put a person at risk of limited or restricted participation. That risk of restricted participation – in the absence of accommodations – is ‘disability’ as defined by the UN Convention on the Rights of Persons with Disability (CRPD).
The domains of seeing and hearing are handled differently. In many cultures, both glasses/lenses and, to a lesser extent, hearing aids are ubiquitous and in most cases the use of these devices, especially glasses, is able to correct the difficulty almost completely. For this reason they are considered ‘within the skin’ or a part of the person. If, for example, the WG were to ask about difficulty seeing without the use of glasses, the resultant prevalence would be extremely high and would not identify a population at risk of participation restriction. However, in places where glasses or hearing aids are not common, the clause ‘even when wearing glasses’ can be omitted.