Fourier analysis of textural variations in human normal and cataractous lens nuclear fiber cell cytoplasm

Variations in cytoplasmic texture of human normal and cataractous lenses were investigated with Fourier analysis. Fixed Vibratome sections of six normal transparent human lenses (age range 55-72 years) and six nuclear cataractous lenses (age range 66-89 years) were examined using transmission electron microscopy. Images were taken of the fiber cell cytoplasm and examined using linear optical density scans, Fourier transforms and autocorrelation analysis. The cytoplasm of normal human lenses was found to be smooth and homogeneous. Radially-averaged plots of Fourier transforms revealed a broad band of intensity over the range of 15-50 nm. Four of the six cataracts also had homogeneous cytoplasm without substantial density variations. Fourier transforms and radially-averaged plots were similar to those of the normal, although slightly lower in intensity for components/=200 nm. Autocorrelation analysis supported the data obtained by Fourier transforms. Radially-averaged plots of the autocorrelation resultant displays detected only small structural units in the normal and non-textured cataractous cytoplasm, whereas larger structural units were detected in the textured cataractous cytoplasm. The appearance of the textured cataractous cytoplasm suggests that redistribution or loss of protein may be the cause of density variations in these types of cataracts. Importantly, these results indicate that some nuclear cataracts do not contain spatial fluctuations in the cytoplasm large enough to cause significant light scattering. The data suggest that nuclear cataractogenesis is a multi-factorial process involving minor alterations in cellular structure.