The global prevalence of horizontal strabismus: A systematic review and meta-analysis with a focus on ethnic variation

The prevalence of the 2 types of horizontal strabismus, esotropia and exotropia, varies considerably between studies.This variability has been attributed to factors such as geography/environment, research methodology, age of study subjects, and/or ethnicity.Comprehensive estimates of regional and global prevalences of esotropia and exotropia are lacking, making it difficult to recognize true patterns, trends, and etiologies.We compile prevalences and ratios of esotropia to exotropia from 315 population-based studies and 374 clinic-based studies.We analyze data to assess effects of ethnicity, geography, age, and we identify generational changes of horizontal strabismus.Major ethnicities differ in patterns and ratios of esotropia and exotropia prevalence, not only in Caucasians and East Asians, but also Latinos/Hispanics, South Asians, Africans, and Native Americans.Compared to populationbased studies, clinic-based studies underestimate exotropia J o u r n a l P r e -p r o o f Sweden, 18,315,417,618 and the UK.