Energy dispersive x-ray analysis of the cornea. Application to paraffin sections of normal and diseased corneas.

The distribution of chemical elements in the normal human cornea was studied by energy dispersive x-ray analysis and scanning electron microscopy of routinely prepared paraffin sections. Calcium, phosphorus, and sulfur were consistently present in quantities above background and varied in concentration regionally. Analysis of fresh-frozen tissue, an approximation of the in vivo state, gave a similar elemental profile to paraffin sections, except for the loss of diffusable electrolytes in the latter. After fixation, S was the most abundant element and was highest in Descemet's membrane. Corneas with granular, lattice, macular, and Fuchs' endothelial dystrophies, band keratopathy, and spheroidal degeneration were also examined. Characteristic patterns of abnormal S and Ca distribution were found in each of the dystrophies. The relative proportions of Ca, P, and S gave diagnostic profiles for distinguishing band keratopathy and spheroidal degeneration.