Designing a tool for measuring determinants of eye self-care and evaluating its psychometric properties.

Background: Eye care is crucial for maintaining healthy vision. This study aimed to design a determinants assessment instrument related to eye self-care in the student community and evaluate its psychometric properties.

Materials and methods: The present mixed-method cross-sectional study was conducted in two sections using Creswell and Plano Clark methods for instrument development. The study was conducted in Isfahan, Iran, in 2021. The first section (textual analysis and qualitative research) explained and developed the instrument's fundamental items. This section included in-depth, semi-structured interviews with 21 students and eight experts. In the second, the psychometric properties of the designed instrument have been evaluated. Twenty students assessed the instrument's qualitative and quantitative face validity. The instrument's content was measured by computing the content validity ratio and content validity index. In addition, exploratory factor analysis (performed on 251 students) was used to establish construct validity. Internal and test-retest reliability was determined using Cronbach's alpha and intraclass correlation coefficients (ICC), respectively.

Results: During face and content validity assessment, a 39-item questionnaire was finalized. Exploratory factor analysis led to the extraction of seven factors, including "perceived self-efficacy and self-regulation," "outcome expectation," "perceived barriers," "motivation," "perceived susceptibility," "normative beliefs," and "perceived severity." The seven extracted factors explained 48.6% of the total variance. Cronbach's alpha was obtained to be 0.780, indicating good internal consistency, and the ICC for the total score of the questionnaire was 0.892 (95% confidence interval: 0.822-0.944), indicating excellent test-retest reliability.

Conclusion: Our developed questionnaire was a valid and reliable instrument for assessing eye care determinants among students, a vulnerable population afflicted with eye defects and disorders.