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Laurence S. Lim, Xianfeng Yang, Gus Gazzard, Seang Mei Saw, Anqi Qiu; Variations in Eye Volume, Surface Area, and Shape with Refractive Error in Young Children by Magnetic Resonance Imaging Analysis. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3058.
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© ARVO (1962-2015); The Authors (2016-present)
Ocular shape in myopia is poorly understood, particularly in children. The aim of this study is to determine variations in eye volume, surface area, and shape with refractive error in young children using a three-dimensional (3D) magnetic resonance imaging (MRI) model.
A subset of Singaporean Chinese boys enrolled in the population-based Strabismus, Amblyopia, and Refractive Error in Singapore (STARS) study underwent MRI using a 3-Tesla whole body scanner with a 32-channel head coil. A 3D coordinate system for each eye was generated using atlas-based segmentation followed by multiple iterative least square error estimation. Eye volume and surface area were measured. Eye shape was assessed qualitatively from the 3D models, and quantitatively by measurement of the axial length (AL), horizontal width, and vertical height along the cardinal axes.
134 eyes of 67 subjects (mean age 49.3 ± 9.8 months) were analysed. The mean spherical equivalent (SE) refraction was 0.65 ± 0.92D (range -2.31 to 4.13D). In age-height adjusted models, more myopic SE was associated with larger eye volume (-300.64(95% confidence interval -179.13, -422.14)mm3/D; p<0.001) and surface area (-51.10(-29.71, -72.50)mm2/D;p<0.001). In myopic subjects (SE≤-0.5D), more myopic SE was associated with longer AL (-1.19(-0.35, -2.02)mm/D;p=0.01) but not width or height. In non-myopic subjects, more myopic SE was associated with longer AL (-0.38(-0.15,-0.59)mm/D), width (-0.59(-0.41, -0.77)mm/D) and height (-0.42(-0.20, -0.64)mm/D) (p≤0.001 for all). More myopic SE was associated with larger differences between the AL and width (r = -0.87, p=0.003) in myopic but not non-myopic subjects.In 3D models, myopic eyes conformed to an axial elongation model with a prolate profile in the axial plane while non-myopic eyes showed global expansion. Myopic eyes also showed asymmetric enlargement with greater protrusion in the posterior infero-temporal region
Eye volume and surface area increase with myopia in young children. Axial globe enlargement occurs in myopic eyes leading to a prolate shape, whereas non-myopic eyes enlarge globally in length, width and height. These differences are evident even in the early stages of myopia.
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