Collagen crosslinking in keratoconus.

The examination of reducible collagen crosslinks in keratoconus cornea revealed the presence of lysinonorleucine in amounts far greater than in normal age-matched corneas. There was no indication of decreased hydroxylysine levels in keratoconus, and there were no clinical indications of a generalized connective tissue disorder. The abnormal levels of dehydrolysinonorleucine in the tissue may represent a change in hydroxylation of selected lysyl residues of normal collagen or the synthesis of abnormal collagen, perhaps an unusual type.