Table 7 Guiding principles for retinal screening leaflet intervention design

Readability and comprehension: content to be written to acceptable (health) literacy standards, with minimal technical or medical terminology [59, 60].

Scope: the scope of intervention messages to be restricted to targeting individual-level, modifiable behavioural determinants.

Framing: despite long term benefit, retinal screening can be considered a high-risk behaviour due to the potential for immediate DR diagnosis [61]. Loss-framed messages are effective in promoting engagement with high-risk behaviours and will be used in this leaflet [25]. The majority of headings to be framed as questions to engage the reader while minimising any potentially defensive reaction [62].

Sequence: content to follow the logical order of reading. In order to balance loss-framed messages against the high levels of diabetes-related distress and anxiety experienced by young adults with T2D [20, 40], potentially threatening content to be immediately followed by an empowering or reassuring statement.

Use of quotes: in recognition of the subtle aspects of social influence, where an individual’s’ beliefs are influenced by those accepted and encouraged by the majority [63], quotes from similar others to be used to reinforce key persuasive messages. All quotes to be sourced verbatim from interview study with descriptors (age and diabetes duration) included to reinforce group membership.

Credibility: quote descriptors within the leaflet to reflect demographic characteristics of the priority population to prompt identification with a credible source. Similarly, logos of leading diabetes and eye health organisations that had contributed to the content to be included to enhance credibility of information. Important yet necessary negative information (e.g. discomfort associated with mydriasis, time required to recover clear vision) to be included to provide balance.

Graphics and imagery: to reflect the demographic characteristics of the priority population (e.g. young adults from a range of ethnicities, with and without children). National interpreter symbol to indicate availability of language assistance services to those with limited English proficiency [64].