Multilamellar bodies as potential scattering particles in human age-related nuclear cataracts

PURPOSE: To characterize within human age-related nuclear cataracts rare sp herical objects covered by multiple membranes, termed multilamellar bodies (MLBs). METHODS: Adult human normal, transparent lenses were obtained from eye bank donors and age-related nuclear cataracts were obtained immediately after e xtracapsular extraction. Each sample was Vibratome sectioned fresh into 200 mum thick sections that were fixed and embedded for light or electron micr oscopy. Confocal images were recorded from sections stained with the lipid soluble dye, DiI. RESULTS: Light micrograph montages of the equatorial plane containing the f etal and embryonic nuclei were examined. Rare, but distinct, circular 1-3 m um diameter objects were observed consistently in the cataracts. These obje cts did not appear to be components of the complex intercellular interfaces . Serial sections indicated that the objects were spherical, or contained a spherical component. For about 20,000 fiber cell cross-sections in each le ns, the frequency of MLBs was 10 times higher in cataracts than in the norm al lens nuclei. Although extensive searching with the electron microscope w as necessary, the size, circular profile and multiple layers of thin (5 nm) membranes easily identified the MLBs. Interiors of the MLBs displayed vari able textures. Confocal images indicated that the coverings were enriched i n lipid compared to the adjacent plasma membranes. The calculated density o f the MLBs in the cataractous nuclei was about 3800/mm(3), which represents a volume fraction of 0.00003. CONCLUSIONS: Because the MLBs are large compared to the wavelength of light , display interiors with variable staining textures and have lipid-rich cov erings, they appear to be ideal candidates for large scattering particles t hat may contribute to the forward light scattering in nuclear cataracts.