Internal astigmatism and risk factors in Tibetan schoolchildren: The Lhasa Childhood Eye Study.

Conclusions: The study first investigated the prevalence and internal relationship of astigmatism components under cycloplegia in Tibetan children on plateau areas of China. We found a higher prevalence of refractive (RA) and corneal astigmatism (CA) in Lhasa children and certified the compensation of internal astigmatism (IA), which might be associated with myopic progression.

Objective: This study aimed to investigate the prevalence and related risk factors of RA, CA, and IA and evaluate compensation and associated influence factors of IA in Lhasa Tibetan children.

Methods: This was a school-based cross-sectional study. Stratified random clustering was used to recruit 1751 Tibetan children with a mean age of 7.90 ± 0.48 years from schools in Lhasa, China. Cycloplegic autorefraction was conducted, and ocular biometrics were examined.

Results: The prevalence rates of RA, CA, and IA were 18.73, 72.53, and 40.72%, respectively, with the diagnosis criteria ≥1.00 D. With-the-rule was the main type of RA (70.05%) and CA (91.93%), whereas the against-the-rule was predominant in IA (79.67%). Compared with the reference group (spherical equivalent range, 0.51 to 1.00 D), mean RA and CA increased with more hyperopic and myopic refractions, and mean IA was significantly lower only in myopia and emmetropia groups. Girls had a higher incidence of CA and IA than boys. Internal astigmatism was negatively correlated with CA in the vertical/horizontal vector ( J0 ) and oblique vector ( J45 ). The majority of IA compensated for RA in different degrees (95.25% in J0 and 66.43% in J45 ) and no compensation accounted for a higher proportion in myopic children (10.47% in J0 and 5.76% in J45 ).

Conclusions: The prevalence of RA and CA in Tibetan children from Lhasa was higher than reported in most previous studies. The compensation of IA in reducing CA was prominent, and the function could decrease with the myopic progression.