Factors Influencing the Transition From Physiological Hyperopia to Myopia in Children: Protocol for a Prospective Nested Case-Control Study.

Background: The early onset of myopia in children has become a critical public health issue that requires urgent attention. Notably, high myopia-related retinal diseases have emerged as the leading cause of irreversible blindness in adults in certain regions of China. Physiological hyperopia, as a protective factor and one of the strongest predictors of myopia development, plays a key role in delaying the progression of early-onset myopia and reducing the risk of high myopia in adulthood. However, the dynamic changes, critical turning points, and factors contributing to the rapid regression of physiological hyperopia during childhood remain unclear. Objective: This study aims to explore the key influencing factors for children's physiological hyperopia fading and myopia onset, as well as the protective mechanisms of physiological hyperopia against myopia. Methods: This was a prospective nested case-control study. Our research team previously established a prospective cohort of 2109 preschool children, aged 3 to 6 years, through cluster sampling in 22 kindergartens in Haidian District, Beijing, and completed a 3-year follow-up. Building on this cohort, this study adopts a prospective nested case-control design. We will continue to follow up this cohort with a 3-year longitudinal study, tracking children aged 6 to 9 years. During the 3-year follow-up period, participants will undergo annual eye examinations and complete questionnaires regarding their living habits and environment. The primary outcome is incident myopia, while secondary outcomes include the prevalence of myopia and the changes in various ocular biological parameters. The study received ethics approval on April 7, 2024, from the Ethics Committee of Beijing Tongren Eye Center, Beijing Tongren Hospital (TREC2024-KY034) and was registered on July 5, 2024. Results: Participant recruitment began on July 10, 2024, and is expected to be completed by December 31, 2026. As of February 2026, recruitment is ongoing, and the final results are expected by December 2026. Conclusions: This prospective nested casecontrol study investigates the dynamic changes and regression patterns of physiological hyperopia in school-aged children and evaluates the associations between ocular biometric parameters and the onset of myopia. The findings are expected to support standardized myopia screening, inform clinical interventions, and provide evidence-based guidance for government policies on myopia prevention and control in young children.