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Four patients, each of whom had had an uncomplicated cataract extraction, were examined because of an apparent epithelialization of the anterior chamber. In each instance, the diagnosis was later verified histopathologically. The involved eye was photographed with the clinical specular microscope and the endothelial photomicrographs were analyzed. It was noted that considerable endothelial cell loss had occurred, as evidence by the larger size of the remaining cells. Endothelial cells were present but they were grossly abnormal well below the demarcation line visible with the slit-lamp biomicroscope. These in vivo observations support the thesis that damage to the corneal endothelium is a necessary factor for epithelial invasion of the anterior chamber.

A technique and apparatus for observing and photographing the corneal endothelium in vivo at a magnification of approximately times 200 is described. The method is suitable for animal experimentation and for diagnostic observation and clinical research in humans.

The corneal endothelium in 12 cases of keratoconus was examined with the clinical specular microscope. There appeared to be an increase in cellular pleomorphism with many cells considerably smaller than normal distributed throughout the endothelial cell population. There were also many large, elongated cells whose long axis showed a definite tendency to assume a similar directional orientation. The long axis of these cells seemed oriented toward the apex of the cone, and the cells appeared to have been stretched by the ectatic process. Many endothelial cells contained dark intracellular structures. Their significance is unknown. The single cornea in this series with a history of acute hydrops contained a localized area in which the endothelial cells were seven to ten times larger than normal. This suggests that rupture of the endothelium and Descemet's membrane, responsible for the acute edematous process, occurs at this site, and that the adjacent cells enlarged to fill the defect.

The clinical specular microscope shows the morphological appearance of the endothelium in normal and abnormal corneas. This instrument resolves the endothelial mosaic of the normal cornea into a quasiregular pattern of contiguous cells having well-defined cell boundaries. Cell size varies over a wide range in a number of disorders, and endothelial cells may assume shapes that are substantially different from their usual hexagonal appearance. Cell boundaries are dark and most commonly appear as a straight, narrow line. However, other types of cell boundaries, collectively referred to as doubled boundaries, have been encountered. Cell boundaries normally intersect in a manner that results in three angles of intersection, each approximately 60 degrees, but variations from this pattern are seen. A number of noncellular structures also can be seen in the endothelial zone.

The clinical specular microscope yields a corneal endothelial image. Depending on the slit width of the illumination source, a typical endothelial photomicrograph contains three or four distinct zones. The appearance of the boundary between the endothelial cell pattern and the adjacent dark zone, called the dark boundary, reflects the configuration of the endothelial cell-aqueous humor interface and provides important information about the posterior corneal surface.