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Liqin Jiang, Xiangtian Zhou, Bjorn Drobe, David Troilo; Eye Shapes Measured by MRI are Different in Different Age Groups of Chinese School Children with Similar Refractive States. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3626.
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Different eye shapes are associated with differences in refractive error, but the nature of the relationship between the eye shape and the development of refractive error, particularly myopia, is unclear. This cross sectional study was conducted to compare eye shape and refractive state in emmetropes and myopes at different ages, in order to determine how eye shape changes with age and development of refraction.
We recruited 39 children (mean±se: 11.5±1.0yrs) from primary schools and 28 adolescents (17.7±1.1yrs) from high schools. Subjects were categorized as emmetropes (EM, +0.30±0.08 D) or low myopes (LM, -1.20±0.08 D). Only data from the right eyes were used for analysis. Axial eye length and eye shape were measured from MRI sections through the center of the eye in the transverse (horizontal) and sagittal (vertical) planes. The ratio of equatorial diameter (EQ) to the vitreous chamber (VC) was used as an eye shape index, and the symmetry of eye shape was determined from measures of vitreous chamber depth at 10 deg increments from the posterior nodal point in the transverse and sagittal planes.
The VC depth measured on the AP axis from MR images in the sagittal plane was correlated with that in the transverse planes (R=0.7, p<0.05). The index of overall eye shape indicated that emmetropes were significantly more oblate than myopes in the younger group (0.967±0.016 vs 0.986±0.026, p<0.01), but there was no difference in the older adolescent group (0.997±0.031 vs 1.004±0.022, p>0.05). VC depth in the horizontal plane showed significant nasal-temporal asymmetry, (VC depth is greater on the temporal side) in emmetropes and myopes at both ages examined. However, the VC depth in the vertical plane showed a larger superior-inferior asymmetry (superior VC depth is greater) in children than in adolescents (e.g. at off-axis 50 deg, 1.23 vs 0.21, p<0.01). Myopic children had significantly deeper superior VCs than emmetropes (EM vs LM at 50 deg, 1.46±0.26 vs 0.23±0.29mm, p<0.001) that was not seen in the adolescent group (-0.48±0.26 vs -0.68±0.20mm, p>0.05).
Asymmetry in eye shape associated with myopia in children was not apparent in adolescents. Further studies, including longitudinal tracking of eye shape in emmetropes and myopes are needed to confirm that this is a developmental change.
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