Prevalence, incidence and risk factors of strabismus in a Chinese population-based cohort of preschool children: the Nanjing Eye Study.

Aims: To evaluate the prevalence, incidence and their related risk factors of strabismus among preschool children in China.

Methods: Children born between September 2011 and August 2012 in Yuhuatai District of Nanjing were invited to participate in the Nanjing Eye Study for a comprehensive eye examination annually since 2015. The data presented in this paper were obtained from 2015 to 2017, when these children grew from the age of 3 to 5 years. Eye examinations included visual acuity, anterior segment, posterior segment, refraction, and ocular alignment and motility. Risk factors were evaluated using univariable and multivariable logistic regression models for prevalent and incident strabismus.

Results: In 2015, a total of 2018 children (87.7% response rate) of 2300 eligible preschoolers completed the baseline eye examination when they were 3 years old. Among the 2018 participants, 50 had strabismus (prevalence rate, 2.48%). In multivariable analysis, prevalent strabismus was independently associated with parental strabismus history (OR=11.60, p<0.001), hyperopia (OR=6.22, p<0.001), prematurity (OR=3.07, p=0.01) and astigmatism (OR=2.15, p=0.04). Among 1766 children followed up for 2 years, 63 developed strabismus (annual incidence rate, 1.78%), of whom 57 had exotropia and 6 had esotropia. In multivariable analysis, incident strabismus was significantly associated with parental strabismus history (OR=5.55, p=0.04) and prematurity (OR=3.77, p<0.001).

Conclusions: In this population-based cohort study, we found a higher incidence of strabismus and a higher exotropia:esotropia ratio than previous studies in preschool children. Parental strabismus history and prematurity were associated with a higher risk for both prevalent and incident strabismus.