Descriptive anatomy of the ageing process of the human cornea as visualized by SEM.

Two corneas from elderly patients (87 & 95 years) were studied by SEM and the results compared with in-vitro aged corneas and a keratoconus. The detachment of epithelial cells as part of a cell renewal process leads to loss of epithelium and exposure of Bowman's membrane. The degenerative process in the endothelium leads to porosity and loss of the endothelial cell membrane and finally to (partial) loss of the endothelial cell layer. The start of such a degenerative process is marked by the formation of liquid-filled blebs. The balance of degeneration versus regeneration is clearly biased in favour of the degenerative process, because the cells are not able to produce sufficient collagenous material to cover the denuded areas.