Posterior collagenous layer of the cornea. Ultrastructural classification of abnormal collagenous tissue posterior to Descemet's membrane in 30 cases
G. O. Waring 3rd
We studied the transmission electron microscopy of the abnormal collagenous
tissue posterior to Descemet's membrane in 30 human corneas that
represented 19 different diseases. We named this abnormal tissue the
"posterior collagenous layer" of the cornea and classified it into three
morphologic types: (1) banded posterior collagenous layer, characterized by
110-nm wide-spacing material, (2) fibrillar posterior collagenous layer,
characterized by loose meshwork of collagenous fibrils 20 to 30 nm in
diameter, and (3) fibrocellular posterior collagenous layer, characterized
by fibroblasts in connective tissue. The published ultrastructural studies
of 88 corneas that represented 13 different clinical disorders fit this
classification well. The posterior collagenous layers often formed multiple
lamellae, but no pattern was invariably associated with a specific clinical
disorder. We think these multiple layers represent successive periods of
deposition of collagen by a stressed corneal endothelium and provide a
lifelong record of senescent and pathologic events.
