Constant Volume of the Human Lens and Decrease in Surface Area of the Capsular Bag during Accommodation: An MRI and Scheimpflug Study
Constant Volume of the Human Lens and Decrease in Surface Area of the Capsular Bag during Accommodation: An MRI and Scheimpflug Study
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DOI：
10.1167/iovs.08-2124
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发表时间：
2009-01-01
影响因子：
4.4
通讯作者：
Heethaar, Rob M.
中科院分区：
文献类型：
--
作者：
Hermans, Erik A.;Pouwels, Petra J. W.;Heethaar, Rob M.
目的.囊袋的表面积的变化和透镜的体积的变化可以指示在调节期间透镜的形状的变化是由于透镜材料的可压缩性还是弹性。使用3D磁共振成像（MRI）对年龄在18岁至35岁之间的5名健康受试者的透镜的完整形状进行成像。将横截面形状的参数表示拟合到透镜的边缘，所述边缘用Canny边缘滤波器确定。基于将透镜划分为八个部分，参数化形状使得可以计算作为调节的函数的平均横截面积、体积和表面积。使用校正的Scheimpflug成像来验证用MRI获得的结果。MRI和Scheimpflug测量结果在中央前后曲率半径和厚度方面无显著差异。根据Helmholtz调节理论，随着调节的发生，前后曲率半径和赤道直径减小，透镜厚度增加。在调节过程中，平均横截面积增加，表面积减少。然而，没有发现透镜体积的显著变化。保持透镜体积意味着内部人体透镜材料可以被假定为不可压缩的并且正在经历弹性变形。此外，表面积的变化表明囊袋也经历弹性变形。（Invest Ophthalmol维斯科学。2009; 50：281-289）DOI：10.1167/iovs.08-2124
PURPOSE. A change in surface area of the capsular bag and a change in volume of the lens can indicate whether a change in the shape of the lens during accommodation is due to the compressibility or the elasticity of the lens material.METHODS. 3D magnetic resonance imaging (MRI) was used to image the complete shape of the lens in a group of five healthy subjects between 18 and 35 years of age. A parametric representation of the cross-sectional shape was fitted to the edges of the lens, which were determined with a Canny edge filter. Based on a partition of the lens into eight parts, the parametric shape makes it possible to calculate the mean cross-sectional area, the volume, and the surface area as a function of accommodation. Corrected Scheimpflug imaging was used to validate the results obtained with MRI.RESULTS. No significant difference in central anterior and posterior radius of curvature and thickness was found between the MRI and Scheimpflug measurements. In accordance with the Helmholtz accommodation theory, a decrease in the anterior and posterior radius of curvature and equatorial diameter and an increase in lens thickness occurred with accommodation. During accommodation, the mean cross-sectional area increased and the surface area decreased. However, no significant change in lens volume was found.CONCLUSIONS. The preservation of lens volume implies that the internal human lens material can be assumed to be incompressible and is undergoing elastic deformation. Furthermore, the change in surface area indicates that the capsular bag also undergoes elastic deformation. (Invest Ophthalmol Vis Sci. 2009; 50: 281-289) DOI: 10.1167/iovs.08-2124