Hyperopic reserve depletion and myopia burden among primary school students in Xingtai, China, 2 years post-covid-19: a cross-sectional study with refraction validation

Abstract

Myopia has become a global public health crisis with an annual economic burden of up to $202 billion. Hyperopic reserve (HR) plays a pivotal role in myopia prevention, as excessive near-work in children depletes physiological HR, accelerates emmetropization, and leads to early myopia onset. Long term COVID-19-related home confinement increased screen time and reduced outdoor activity. This cross-sectional study aimed to investigate HR status and myopia prevalence among primary school students in Xingtai (a representative medium-sized Chinese city with ~ 1 million urban population) two years after the COVID-19 outbreak, and to evaluate the impact of threshold adjustment on the diagnostic performance of non-cycloplegic refraction. A total of 1022 eligible students from 10 randomly selected primary schools underwent comprehensive ocular examinations, including cycloplegic refraction (gold standard for myopia diagnosis). The overall myopia prevalence was 36.50%, with 50.68% of students having inadequate HR and only 12.82% having adequate HR. Myopia prevalence increased significantly with grade, rising from 11.87% (Grade 1) to 65.79% (Grade 6) ( P < 0.0001). Non-cycloplegic refraction overestimated myopia prevalence compared to cycloplegic refraction (OD: 43.93% vs. 32.88%; OS: 40.51% vs. 28.86%; all P < 0.0001). Adjusting the non-cycloplegic spherical equivalent refraction (SER) threshold to − 0.685 D significantly improved diagnostic performance for myopia (OD: 90.90% accuracy; OS: 91.29% accuracy). However, non-cycloplegic refraction cannot reliably distinguish hyperopic reserve adequacy via threshold-based stratification across all age groups. These findings describe the current status of myopia burden and hyperopic reserve depletion in this post-pandemic pediatric survey. Threshold-adjusted non-cycloplegic refraction demonstrates favorable diagnostic performance for large-scale myopia screening, while cycloplegic refraction remains essential for accurate hyperopic reserve assessment.