The biometric parameters of aniso-astigmatism and its risk factor in Chinese preschool children: the Nanjing Eye Study 

Abstract Backgrounds: Aniso-astigmatism may hinder normal visual development in preschool children. Knowing its prevalence, biometric parameters and risk factors is fundamental to children eye care. The purpose of this study was to determine the biometric components of aniso-astigmatism and associated maternal risk factors in Chinese preschool children. Methods: In the population-based, prospective cohort Nanjing Eye Study, children were measured for noncycloplegic refractive error using an autorefractor and for biometric parameters using an optical low-coherent reflectometry. The difference of total astigmatism (TA) between both eyes was calculated using cylinder power (non-vectorial aniso-TA was defined as ≥1.00 Dioptre Cylinder [DC] between both eyes) and by vector analysis (vectorial aniso-TA was defined as a difference of ≥0.5 in J0 or J45 between both eyes which is equivalent to 1.00 DC). The prevalence of aniso-TA was presented. Interocular biometric parameters were compared between with vs. without aniso-astigmatism group. In addition, risk factors were determined using multivariate logistic regression model. Results: Of 1131 children (66.90±3.38 months, 53.31% male), the prevalence of non-vectorial aniso-TA was 1.95% (95% Confidence Interval (CI)=1.14%-2.75%), while the prevalence of vectorial aniso-TA was twice as common as non-vectorial aniso-TA, neither varying with sex or age. With aniso-TA eyes were more asymmetric in axial length and corneal curvature radius than without aniso-TA eyes. In multivariate logistic regression model, 5-min Apgar score less than 7 was significantly associated with higher risk of aniso-TA (vectorial aniso-TA: Odds Ratio (OR)=6.42, 95%CI=2.63-15.69, P<0.001; non-vectorial aniso-TA: OR=4.99, 95%CI=1.41-17.68, P=0.01）. Being twin or triple was significantly associated with higher risk of vectorial aniso-CA (OR=2.43, 95%CI=1.05-5.60, P=0.04). Pre-term delivery (OR=2.60, 95%CI=1.09-6.15, P=0.03) and post-term delivery (OR=3.61, 95%CI=1.31-9.96, P=0.01) were significantly associated with higher risk of vectorial aniso-CA. Conclusions: Both corneal curvature radius and axial length asymmetry were correlated with aniso-TA. Children with 5-min Apgar score<7 were more likely to have aniso-TA, while twin or triple, pre-term or post-term delivery were more likely to have vectorial aniso-CA.