Objective: To examine the 3-dimensional collagen fibril organization in the Bowman layer of keratoconus corneas.
Methods: Eight keratoconus corneas, 8 corneas with other diseases, and 5 normal human corneas were studied. A cell maceration method in combination with scanning electron microscopy was used to examine the collagen network in the Bowman layer.
Results: In normal corneas, the surface of the Bowman layer was smooth and collagen fibrils were regularly arranged. By contrast, sharply edged defects in the Bowman layer were found in keratoconus corneas. Lattice-like configurations of the ruptured Bowman layer and collagenous scar tissue were observed, to varying degrees, in all keratoconus corneas examined. None of the other diseased corneas exhibited the ruptures.
Conclusions: Scanning electron microscopy demonstrated alterations in the Bowman layer specific to keratoconus. Fragmentation of the Bowman layer may be an early change leading to keratoconus conditions.