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P.J. Foster, D. Uranchimeg, P.–S. Lee, D. Patel, S. Wickremasinghe, T.–Y. Wong, B. Dineen; The Distribution of Axial Length Among Young Adults in Urban and Rural Regions Of Mongolia . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4627.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To compare distribution of axial length of the globe of young adults aged 20 to 39 years living in urban and rural regions of Mongolia. Methods: The electoral register was used as the sampling frame. Ulaanbaatar city was selected as the urban study site, and Selenge aimag was chosen as rural. Approximately equal numbers of men and women aged 20–29 and 30–39 were identified by stratified, clustered random sampling, with a total of 375 people chosen in each area. Axial length (AL) was measured using A–mode ultrasound. Visual acuity and refraction was also assessed. Results:A total of 568 (75.7%) of subjects were examined. Mean axial length (AL) was 23.35 mm (95% CI: 23.27, 23.43). Subjects in the urban area were 2 cm taller and 3 Kg heavier than the rural population (P= 0.02). Five times more urban residents had an education to college level, compared with those in the rural environment (P< 0.001). The ratio of those with very low income in rural to urban groups was more than 3:1 (P< 0.001). There was no significant difference in AL between 20’s and 30’s in the rural area (23.23 vs. 23.15, P= 0.77), however, the AL was significantly longer among young people in the city (20’s: 23.66 vs. 30’s 23.37, P=0.02). Mean AL was significantly longer in people aged 20–29 compared with those 30–39 years old in the city (P= 0.03). The same difference was not present in the rural group (P= 0.46). Multivariate analysis identified height (P< 0.001) and educational achievement (P< 0.001) as significantly associated with AL. Urban or rural residence was of borderline significance (P= 0.054). A unit increase in educational achievement (primary, secondary and college) was associated with a 0.36 mm increase in axial length. For a 10cm increase in height, there was a corresponding 0.27 mm increase in axial length. Conclusions: These data indicate that AL is significantly longer in city–dwelling young adults in Mongolia. In part this is attributable to their greater height. The link with educational achievement may reflect the recognized association with near work and myopia. It seems likely that other important associations explaining AL differences between urban and rural populations remain to be identified.
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