Eye Examinations as a Gold Standard to Evaluating Survey Instruments

The schools will be visited to announce this project on survey experiment and measuring visual acuity, for which all participants will receive free eye examinations. After receiving consent/assent, two data collection strategies will be applied in this survey - DCV and ICV, to identify individual perceptions of vision. In the arm of ICV, the self-assessment of vision (SAV) is listed before the vignette questions; however, in the arm of DCV, the self-assessed vision (PSAV) is listed after the vignette questions to estimate priming effect. With randomization prior to administration of survey, 50% of the students will be enrolled in "direct comparison against vignettes" (DCV) and another 50% for "implied comparison against vignettes" (ICV). Each participant will self-administer the survey. The objective measure of vision will be set up in a vacant classroom with assistance from members of the Health Center Jingning County. DCV, ICV, SAV, and PSAV are estimated from randomized survey questionnaires. Objectively measured vision is from simplified Snellen chart.

Measures - All subjects will be asked to respond to the questions about vision acuity without glasses or contact lenses for themselves and these hypothetical scenarios. Information collected through the survey includes self-assessed vision, vignettes, clusters (school, grade, and class), whether the subjects wear glasses or contact lenses, and two demographic variables (age and sex).

Self-assessed vision - Data of self-assessed vision is collected by asking students to think about their own vision without glasses or contact lenses. Specifically, each student was asked to respond to this question: "at the present time, would you say your distance eyesight is excellent, good, fair, poor, or very poor?" Vignettes - The DCV questionnaire asks subjects to jointly evaluate their own vision and vignette situations; meanwhile, the ICV questionnaire asks subjects to conduct single evaluation of vignette questions. Even though subjects in ICV questionnaires were not asked to compare their visual acuity with the hypothetical person Zhang, the experimenter could conduct the comparison through data analysis. Accordingly this approach is named the "indirect comparison against vignettes" (ICV).

For example, in the DCV questionnaire, the subjects will be asked to respond to the following question:

Sitting in the last row in the classroom, [Xiao Zhang] does recognize teacher's faces clearly but cannot identify small hand writing on the blackboard clearly. Would you say your distance eyesight is: