Participants and recruitment

OSPs are not informed of participation, thus they will be visited unannounced by USP. We will recruit USPs and train them, implementing interventions in different groups. Figure 1 presents an explicit flow chart of this study.

Flow chart of the study

The study subjects (OSPs and their refraction-ists) must meet the following criteria to be eligible for the study: (1) OSPs in Guangzhou and Inner Mongolia, consisting of general hospitals with ophthalmology department, ophthalmology specialty hospitals or clinics, and optical shops; (2) any personnel providing optometry services, as licensed optometrists and ophthalmologists or not, at the above-mentioned institutions. Exclusion criteria include: (1) providers providing Internet-based services only; (2) providers providing optometry service solely for contact lenses only.

The USPs must meet the following criteria to be eligible for the study: (1) people with refractive error profile of interest (myopia or myopia with astigmatism), and good ocular health; (2) fluent native speakers of the primary language of the district; (3) having a good memory. If the USPs meet any of the following criteria, they will not be eligible for the study: (1) having prior refractive eye surgery or had eye surgery within the last three months; (2) having manifest or intermittent strabismus, or amblyopia; (3) people with any ocular or health conditions that can cause variable spectacle prescription.

We will develop the sampling frame of all OSPs who meet our inclusion and exclusion criteria by crawling the data of Gaode Map, the leading map service App with the advantage of capturing both registered and non-registered optical shops in China. We will select the sample of OSPs with stratified and simple random sampling. Likewise, we will recruit USPs by posting part-time job announcements on campus posters and social media, like WeChat, and also through our existing USP network. The USPs will be paid for participation and reimbursed for other related expenses.

At recruitment, all USPs and their companions must sign the informed consent electronically through a web link sent by our emails. We have obtained a waiver for informed consent from the OSPs as the process may compromise the sample representation due to possible participant self-selection. We meet the criteria of consent waiver for the USP studies as stipulated by the medial ethics: (1) data analysis will only be performed at the aggregated level rather than targeting individual participants; (2) de-identification for the participating individuals and institutions will be fully implemented; and (3) services performed on USPs are not critical services where resources must be protected for the real patients [23].