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Mellisa Hege, Jason CS Yam, Simon Ko, Gabriela Chong, Jeremy Kwok, Laila Mossa-Basha, Shanshan Li, Jingyun Wang; Comparing refractive error distribution in children with Intermittent Exotropia from the Chinese and American Non-Chinese ethnicity. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5227.
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Children with Intermittent Exotropia (IXT) in the West are often emmetropic or low hyperopic (Abrahamsson et al, 1992). However, the prevalence of myopia has been reported to be higher in Chinese ethnicity (Pan et al, 2012). It is possible that Chinese children with IXT are more myopic than children with IXT in the western countries. This study compared the refractive error distribution at the age of detection in children with IXT in Hong Kong to children with IXT in Indiana, USA.
Retrospective cohort study of children with IXT from Hong-Kong (Chinese ethnicity) and Indiana (American Non-Chinese ethnicity: 85% Caucasian and 15% of other races, excluding Chinese). Eligibility criteria included: 3 to 15 years old, diagnosed with IXT, no prior surgery, no Down syndrome or other systematic or genetic conditions, and birth age >36 weeks. Cycloplegic refractive errors at the age of detection culled from medical records were converted to a spherical equivalent (SEQ) in diopters (D). Astigmatism was estimated by the magnitude of cylinder (CYL). Both SEQ and CYLwere analyzed for two age subgroups: a 3- to 7-year-old subgroup and an 8- to 15-year-old subgroup. To compare the SEQ difference between the two groups, an independent t-test was used. Due to the general similarity of refractive error in both eyes in children with IXT, only the results from the right eye were reported.
The study included 156 patients. On average, SEQ is more myopic in the Chinese group than in the American non-Chinese group. The SEQ of Chinese children in two age subgroups were all significantly more myopic than that of American non-Chinese Children (p<0.05, see Table 1). In both Chinese and Non-Chinese groups, the mean SEQ was significantly more myopic in the 8-15 year-old subgroup than in the 3-7 year-old subgroup (P<0.01, Table 1). However, there was no significant difference on the CYL between groups (p=0.6).
Compared to American Non-Chinese children with IXT, Chinese children with IXT are more myopic. Also, older children tend to be more myopic. Such distribution may be associated with the high prevalence of myopia in Chinese ethnicity.
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