The effect of corneal stretch on the endothelium.

A model has been developed to describe the phenomenon of corneal stretch. In the model situation, suction is applied to the corneal surface of the bovine eye. The newly induced corneal shape forces the endothelial layer to stretch and sometimes to tear apart in places. This same type of stretch can be induced when a soft lens is placed on the bovine cornea. We postulate that drying of the soft lens produces a local flow of water from the cornea at the lens periphery with a secondary bowing of the central cornea. These results are confirmed by a decrease in the peripheral keratometry readings with an increase in the central keratometry measurements. The resultant deformation increases the posterior surface area of the cornea thus stretching the endothelium. These reversible/irreversible changes are time/drying dependent. The endothelial effects of corneal bending, as in cataract extraction, radial keratotomy and tight suture placement were investigated. As expected, when these techniques stretch the cornea, the result is endothelial changes.