PURPOSES. To determine axial, vertical, and horizontal eye dimensions in myopi c and emmetropic eyes by using magnetic resonance imaging (MRI) and to relate th ese to different ocular expansion models of myopia develo...PURPOSES. To determine axial, vertical, and horizontal eye dimensions in myopi c and emmetropic eyes by using magnetic resonance imaging (MRI) and to relate th ese to different ocular expansion models of myopia development. METHODS. The int ernal length (cornea to retina), height and width (both retina to retina) were m easured in emmetropic and myopic eyes (up to-12 D) of 88 participants aged 18 t o 36 years. Participants were positioned supine in a clinical MRI scanner. The f ixation target was imaged straight ahead of the subject by an overhead 45°incli ned mirror. Eye images were acquired with a 7.5 cm receive-only radio frequency surface coil. Axial (horizontal through middle of eye) and sagittal (vertical t hrough visual axis) sections were taken with a T1-weighted fast spin-echo sequ ence. RESULTS. With an increase in myopic refractive correction, myopic eyes bec ame much larger in all three dimensions, but more so in length (0.35 mm/D, 95%c onfidence interval CI 0.28-0.40) than in height (0.19 mm/D, 95%CI 0.09-0.29 ) and more so in height than in width (0.10 mm/D, 95%CI 0.01-0.20). Based on h eight and length dimensions,25%and 29%of myopic eyes exclusively fitted global expansion and axial elongation models, respectively. Based on width and length dimensions, 17%and 39%of myopic eyes exclusively fitted the global expansion a nd axial elongation models, respectively. CONCLUSIONS. Although there are consid erable individual variations, in general myopic eyes are elongated relative to e mmetropic eyes, more in length than in height and even less in width. Approximat ely a quarter of the myopic participants fitted each of the global expansion or axial elongation model exclusively. The small proportions are due primarily to t he large variability in the dimensions of emmetropic eyes.展开更多
文摘PURPOSES. To determine axial, vertical, and horizontal eye dimensions in myopi c and emmetropic eyes by using magnetic resonance imaging (MRI) and to relate th ese to different ocular expansion models of myopia development. METHODS. The int ernal length (cornea to retina), height and width (both retina to retina) were m easured in emmetropic and myopic eyes (up to-12 D) of 88 participants aged 18 t o 36 years. Participants were positioned supine in a clinical MRI scanner. The f ixation target was imaged straight ahead of the subject by an overhead 45°incli ned mirror. Eye images were acquired with a 7.5 cm receive-only radio frequency surface coil. Axial (horizontal through middle of eye) and sagittal (vertical t hrough visual axis) sections were taken with a T1-weighted fast spin-echo sequ ence. RESULTS. With an increase in myopic refractive correction, myopic eyes bec ame much larger in all three dimensions, but more so in length (0.35 mm/D, 95%c onfidence interval CI 0.28-0.40) than in height (0.19 mm/D, 95%CI 0.09-0.29 ) and more so in height than in width (0.10 mm/D, 95%CI 0.01-0.20). Based on h eight and length dimensions,25%and 29%of myopic eyes exclusively fitted global expansion and axial elongation models, respectively. Based on width and length dimensions, 17%and 39%of myopic eyes exclusively fitted the global expansion a nd axial elongation models, respectively. CONCLUSIONS. Although there are consid erable individual variations, in general myopic eyes are elongated relative to e mmetropic eyes, more in length than in height and even less in width. Approximat ely a quarter of the myopic participants fitted each of the global expansion or axial elongation model exclusively. The small proportions are due primarily to t he large variability in the dimensions of emmetropic eyes.
