Predicted light scattering from particles observed in human age-related nuclear cataracts using Mie scattering theory
Predicted light scattering from particles observed in human age-related nuclear cataracts using Mie scattering theory
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DOI：
10.1167/iovs.06-0480
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发表时间：
2007-01-01
影响因子：
4.4
通讯作者：
Fowler, W. Craig
中科院分区：
文献类型：
--
作者：
Costello, M. Joseph;Johnsen, Sonke;Fowler, W. Craig
目的。采用米氏散射理论来预测被脂质壳包围的微米级颗粒（称为多层体 (MLB)）的光散射，据报道，该颗粒在人类年龄相关的核性白内障中发生。方法。米氏散射理论适用于随机分布的球形和球状颗粒，其间隔距离远大于入射光的波长。假设核细胞质的折射率为 1.40，颗粒折射率为 1.33 至 1.58，用于计算颗粒半径为 0.05 至 3 μm 以及波长（真空）为 400、550 和 700 nm 的入射光的散射效率。 结果。计算了带涂层的球形颗粒的散射效率与颗粒半径和折射率的表面图。明显的峰和谷确定了产生高和低散射效率的粒子参数组合。小颗粒（<0.3μm半径）在较宽的颗粒折射率范围内具有较低的散射效率。半径为0.6至3μm且折射率比周围细胞质大（或小）0.08至0.10的颗粒具有非常高的散射效率。该尺寸范围与白内障核中的 MLB 很好地对应（平均 MLB 半径为 1.4 μ m），并且在组织中估计有 4000 个颗粒/mm(3) 时，高达 18% 的入射光主要在 20 个前向锥体内散射。结论。计算出的有效散射的球形颗粒的尺寸接近于白内障核中 MLB 的观察尺寸。颗粒折射率与周围细胞质仅相差 0.02 个单位，散射大量光。这些结果表明，在人类年龄相关的核性白内障中观察到的 MLB 可能是前向光散射的主要来源，它会降低精细细节的对比度，特别是在昏暗的光线下。
PURPOSE. To employ Mie scattering theory to predict the light-scattering from micrometer-sized particles surrounded by lipid shells, called multilamellar bodies (MLBs), reported in human age-related nuclear cataracts.METHODS. Mie scattering theory is applicable to randomly distributed spherical and globular particles separated by distances much greater than the wavelength of incident light. With an assumed refractive index of 1.40 for nuclear cytoplasm, particle refractive indices from 1.33 to 1.58 were used to calculate scattering efficiencies for particle radii 0.05 to 3 mu m and incident light with wavelengths (in vacuo) of 400, 550, and 700 nm.RESULTS. Surface plots of scattering efficiency versus particle radius and refractive index were calculated for coated spherical particles. Pronounced peaks and valleys identified combinations of particle parameters that produce high and low scattering efficiencies. Small particles (< 0.3 mu m radius) had low scattering efficiency over a wide range of particle refractive indices. Particles with radii 0.6 to 3 mu m and refractive indices 0.08 to 0.10 greater (or less) than the surrounding cytoplasm had very high scattering efficiencies. This size range corresponds well to MLBs in cataractous nuclei (average MLB radius, 1.4 mu m) and, at an estimated 4000 particles/mm(3) of tissue, up to 18% of the incident light was scattered primarily within a 20 forward cone.CONCLUSIONS. The calculated size of spherical particles that scatter efficiently was close to the observed dimensions of MLBs in cataractous nuclei. Particle refractive indices only 0.02 units different from the surrounding cytoplasm scatter a significant amount of light. These results suggest that the MLBs observed in human age-related nuclear cataracts may be major sources of forward light scattering that reduces contrast of fine details, particularly under dim light.