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Craig Boote, Erin P. Dooley, Kim Nielsen, Jesper Hjortdal, Thomas Sorensen, Jennifer Hiller, Nicholas J. Terrill, Keith M. Meek; An Investigation of Stromal Collagen Organization 12 Years after Penetrating Keratoplasty for Keratoconus. Invest. Ophthalmol. Vis. Sci. 2011;52(14):370.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the detailed arrangement of stromal collagen in a 16mm left post-mortem corneo-scleral button from an individual who underwent 8.0/8.2 mm penetrating keratoplasty (PK) for keratoconus 12 years previously. To our knowledge this is the first study to include structural information on keratoconic tissue from the peripheral cornea and limbus.
Wide-angle x-ray scattering was used to determine the preferential collagen fibril orientation at 0.25 mm intervals across the whole specimen from limbus to limbus. Small-angle x-ray scattering was used to determine the average fibril spacing and index of matrix order along linear scans from corneal centre to limbus at 0.5 mm intervals. The results are compared to equivalent data from normal corneas.
Marked changes in the preferential orientation of fibrillar collagen were observed around the entire graft margin. Increased stromal fibril spacing and reduced matrix order, indicative of corneal scar tissue, were also evident in the wound region. The normal orientation and distribution of collagen fibrils was altered in regions of the peripheral cornea, in some areas extending to the limbus, and potentially relating to keratoconic changes. Collagen parameters within the graft button appeared normal.
Abnormal collagen structure parameters within the graft margin are indicative of incomplete stromal remodelling, and possible long-term mechanical compromise of the tissue. This may be related to some instances of graft failure following PK, which may occur several years post-op. In more severe cases of keratoconus, disruption to stromal architecture may extend beyond the grafted region.
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