INTERLACING AND CROSS-ANGLE DISTRIBUTION OF COLLAGEN LAMELLAE IN THE HUMAN CORNEA

Purpose. The interlacing and cross angles between the collagen lamella e within the human corneal stroma were studied by means of scanning el ectron microscopy (SEM). Methods. For SEM, cells and noncollagenous ex tracellular matrix were removed with 10% sodium hydroxide. Transmissio n electron microscopy (TEM) preparations were performed according to s tandard procedures. The interlacing of lamellae was studied within the limbal, paracentral, and central regions of five different layers. Th e cross angles between the longitudinal axes of adjacent lamellae were measured. The distribution of these angles within defined layers and regions was compared. Special attention was paid to the interlacing of the lamellae. Results. Lamellae split in an anteroposterior direction as well as horizontally into branches and are interlaced by crossing the fissures between the branches. Smaller lamellae cross through clef ts of neighboring lamellae. The cross angles show a high variability o f 1 degrees-90 degrees. With the exception of the limbal region of the layer adjacent to Descemet's membrane, the distribution of cross angl es is similar. A frequent occurrence of cross angles <30 degrees (68%) in this limbal layer can be explained by a pseudocircular orientation (ligamentum circulare corneae) of the lamellae. Conclusion. The prese nt study shows that the three-dimensional organization of the collagen lamellae is characterized by a greater extent of lamellar interlacing than has been assumed until now.