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M. Nagra, B. Gilmartin, N. S. Logan, P. Furlong, E. Wilkinson, K. Singh; Conformation of Sagittal and Axial Meridians in Human Myopia. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3941.
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© ARVO (1962-2015); The Authors (2016-present)
Gilmartin et al. (IOVS 2007; 48:ARVO E-Abstract 1215) used MRI-generated 3D images of the human eye to investigate regional variations in globe conformation in the coronal meridian. Using the same procedures we examine regional variation for sagittal [i.e. superior (S) vs inferior (I)] and axial [i.e. temporal (T)vs nasal (N)] meridians.
Twenty nine young adult subjects (15 with myopia (MSE (D) -5.02±2.50; 14 with emmetropia MSE >-0.50<+0.75) were scanned using a Siemens Trio 3-tesla MRI. Vector co-ordinates of 3D surface polygons (LE only) were assigned to S, I, T and N quadrants, represented graphically in 2D and fitted with a 2nd order polynomial to provide indices of conformation for sagittal and axial meridians. The x2 coefficient (XC) and, by differentiation, maximum distance (MD) from the visual axis were used to provide, respectively, indices of globe bulbosity and symmetry of global expansion. Data were compared for two axial distances: nodal point to 70% (NP-70) and 70 to 100% (70-100).
NP-70: whereas 2-way repeated measures ANOVA for XC failed to reach significance for any condition, MD was highly significant for all conditions bar the inferior vs temporal quadrant. Ascending ranked mean values were I: 12.26±0.54; T: 12.36±0.71; N: 12.92±0.61; S: 13.32±0.53; subjects with myopia exceeded emmetropic subjects in all quadrants by a mean of 0.44mm but this was particularly marked for the temporal quadrant (0.82mm, p< 0.001). 70-100: differences in XC between quadrants was highly significant (p<0.0001) but insignificant for refractive group (p=0.204) and quadrant:refractive group interaction (p=0.83). Ascending ranked values for quadrants were (*-10-3): T:10.2±1.9; I:10.9±1.2; S:11.9±1.6; N: 12.2±1.8 with subjects with myopia showing a significantly increased XC (i.e. greater bulbosity) in the temporal quadrant (p=0.038).
Although subjects with emmetropia and myopia exhibit the same asymmetric profile of global expansion, overall expansion was significantly greater in myopia; for both groups variance in ocular conformation is greater in the posterior segment of the eye than in the intermediate segment.
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