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R. Varma, J. Deneen, J. Lin, M. Ying–Lai, S.A. Cotter, K. Tarczy–Hornoch, M. Borchert, S.P. Azen, MEPEDS Group; Determinants of Refractive Error in Preschool Children: The Multi–Ethnic Pediatric Eye Disease Study . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5451.
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To assess the contribution of corneal curvature and axial length towards the magnitude of refractive error in a sample of children aged 30–72 months.
Participants aged 30–72 months from the Multi–Ethnic Pediatric Eye Disease Study (MEPEDS) – a population–based study of eye disease in infants and young children – underwent a clinical examination including cycloplegic automated refraction, keratometry (using the Nikon Retinomax Handheld Autorefractor/Keratometer), and measurement of axial length (using the Zeiss IOL Master). Multiple regression models were used to identify the determinants of refractive error. Standardized regression coefficients (SRC) were calculated to determine the relative contribution of corneal curvature and axial length both overall and by 6 month age intervals. Partial correlation coefficients (PCC) were also calculated to express the proportion of the total variability in refractive error measurements attributable to the axial length and corneal curvature. All data were adjusted for height of the child.
1753 children aged 30–72 months were included in this analysis (875 female, 878 male; 773 African–American, 980 Hispanic). When stratified by age, there were 290, 237, 222, 269, 244, 297, and 199 children in each of the following 6–month age intervals – 30–36, 37–42, 43–48, 49–54, 55–60, 61–66, and 67–72 respectively. The mean spherical equivalent refractive error, corneal power and axial length was +1.2D (±1.3), 43.2D (±1.5) and 22.1mm (±0.8), respectively. After adjusting for age, gender, race/ethnicity and height, corneal power and axial length explained 70% of the variation in refractive error (overall PCC = 0.7). The PCC's for axial length and corneal power were 0.34 and 0.35, respectively (p<0.0001). The SRC for axial length and corneal power was –0.9 and –0.7. Overall, a 1 mm increase in axial length was associated with a –1.9D (myopic) shift in refractive error. Also, a 1D increase in corneal power was associated in a –0.7D (myopic) shift in refractive error. The magnitude of the SRC and the PCC were similar when stratified by age groups.
In children aged 30–72 months, axial length and corneal power explain approximately 70% of the variation in refractive error and contribute almost equally in explaining the variation. The contributions of axial length and corneal power remain constant over this age range (30–72 months) and play a significant role in determining the magnitude of refractive error.
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