Micromorphology analysis of the anterior human lens capsule.

Purpose: This study aimed to quantify the three-dimensional micromorphology of the surface of the human lens capsule as a function of age.
Methods: Imaging experiments were conducted on whole human lenses received from eight human cadavers (donor age range: 30-88 years). Imaging was performed with an atomic force microscope (AFM) in contact mode in fluid. The porosity and surface roughness were quantified from the height images obtained. A novel approach, based on stereometric and fractal analysis of three-dimensional surfaces developed for use in conjunction with AFM data, was also used to analyze the surface microtexture as a function of age.
Results: The AFM images obtained depict a highly ordered fibrous structure at the surface of the lens capsule, although the overall structure visually changes with age. Porosity and roughness were quantified for each image and analyzed as a function of donor age. The interfibrillar spacing revealed an increasing trend with age, although this result was not significant ( p = 0.110). The root mean square (RMS) deviation and average deviation significantly decreased with increasing age ( p <0.001 for both). The fractal analysis provided quantitative values for 29 amplitude, hybrid, functional, and spatial parameters. All the hybrid parameters decreased with age, although not significantly. Of the functional parameters, the surface bearing index increased significantly with age ( p = 0.017) and the summit height exhibited a decreasing trend with age ( p = 0.298). Of the spatial parameters, the dominant radial wavelength trend moved toward an increase with age ( p = 0.103) and the cross-hatch angle tended toward a decrease with age ( p = 0.213).
Conclusions: Significant changes in the three-dimensional surface microtexture of the human lens capsule were found with age, although more experiments on a larger dataset are needed to conclude this with certainty. The analyzed AFM images demonstrate a fractal nature of the surface, which is not considered in classical surface statistical parameters. The surface fractal dimension may be useful in ophthalmology for quantifying human lens architectural changes associated with different disease states to further our understanding of disease evolution.