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S. Metlapally, S. Johnsen, K. O. Gilliland, M. J. Costello, B. Ramamurthy, P. V. Krishna, D. Balasubramanian; Analysis of Cytoplasmic Texture in Lens Nuclear Fiber Cells in Advanced Cataracts From India. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2015. doi: https://doi.org/.
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The ocular lens nuclear fiber cell lacks organelles, but its cytoplasm contains vital information about the packing and organization of crystallins critical to lens transparency. Previous work has analyzed the cytoplasmic texture in transparent and cataractous lenses of humans and animal models to relate the extent of roughness to the nuclear scattering observed using Fourier analysis. The current work has extended this analysis to advanced Indian cataractous lenses using the Debye-Bueche theory for inhomogeneous materials.
Advanced age-related nuclear cataracts (ages 38-78) and transparent lenses (ages 48, 56) were obtained following extracapsular cataract removal or from the eye bank, respectively, at the LV Prasad Eye Institute. Lens nuclei were Vibratome-sectioned, fixed and prepared for transmission electron microscopy using established techniques. Electron micrographs of the unstained cytoplasm were acquired at 6500X (1024x1024 pixels) and angle-weighted scattering for =400-700 nm was calculated using the Debye-Bueche theory. Electron micrographs from comparable areas in an oxidative damage rat model (OXYS) and normal rat lenses preserved from an earlier study were also used, as they have extremely textured and smooth cytoplasms, respectively.
The Debye-Bueche theoretical approach produces plots that vary smoothly with wavelength and are sensitive to spatial fluctuations in density. The central lens fiber cells from the OXYS rat showed the greatest texture and scattering followed by advanced cataractous lenses from India, both of which represent opaque lens nuclei. The transparent human lenses from India had a smoother texture and less predicted scattering, similar to early cataracts from previous studies. The normal rat lens had a homogeneous cytoplasm and little scattering.
The Debye-Bueche calculations allowed easy comparison of small variations in cytoplasmic texture. The data indicate that this method robustly detects differences between transparent and advanced cataractous human lenses, which may relate directly to the proportion of opacification contributed by the packing of crystallins. The angle-weighted scattering calculated using this method may thus be used to generate a range of curves with which to compare and quantify the relative contribution of the packing of crystallins to the loss of transparency and scattering observed in different cataract grades.
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