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K. O. Gilliland, S. Johnsen, S. Metlapally, M. J. Costello, B. Ramamurthy, P. V. Krishna, D. Balasubramanian; Mie Light Scattering Calculations for Multilamellar Bodies in Indian Age-Related Nuclear Cataract. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2016.
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Multilamellar bodies (MLBs) are lipid-coated spheres (1-4 µm in diameter) found with greater frequency in the nuclear region of human age-related cataracts compared with human transparent lenses. Mie light scattering calculations have demonstrated that MLBs are potential sources of forward light scattering in human age-related nuclear cataracts due to their shape, size, frequency, and cytoplasmic contents, which often differ in refractive index from their surroundings. Previous studies have utilized data from several non-serial tissue sections viewed by light microscopy to extrapolate a volume and have assumed that MLBs are random in distribution (EER 79, 563-76, 2004; IOVS 48, 2007, in press). Currently, confocal microscopy is being used to examine actual tissue volumes from age-related nuclear cataracts and transparent lenses collected in India to confirm MLB shape, size, frequency, and randomness. These data allow Mie scattering calculations to be done with directly observed MLBs in intact tissue.
Whole Indian donor lenses and Indian lens nuclei after extracapsular cataract extraction were immersion fixed in 10% formalin for 24 hours and 4% paraformaldehyde for 48 hours before sectioning with a Vibratome. The 160 µm thick sections were stained for 24 hours in the lipid dye DiI, washed, stabilized in Permount under #1 coverslips, and examined with a Zeiss LSM 510 confocal microscope. Individual volumes of tissue (each approximately 500,000 µm3) were examined using a plan-apochromat 63x oil (na = 1.4) lens.
Analysis of tissue volumes within Indian age-related nuclear cataracts and transparent lenses has confirmed that most MLBs are spherical and 1-4 µm in diameter. Some Indian cataracts and transparent lenses are similar to samples obtained in the US. Others contain as many as 250,000 MLBs per mm3 - more than 50 times that of cataracts collected in the US. Pairwise distribution analysis has revealed that MLBs are found with a distribution that is indistinguishable from a random one. Mie calculations indicate that more than 50% of the incident light can be scattered by the high density of MLBs.
Some advanced Indian cataracts contain many more MLBs than cataracts previously examined in the US. Because of their spherical shape, large size, extremely high frequency, and apparent random distribution, they exhibit high amounts of forward scattering according to Mie light scattering calculations.
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