In this section, we discuss three major reactions of collagen crosslinking important in corneal biology: (1) lysyl oxidase-mediated crosslinking as a post-translational modification of secreted collagen that stabilizes collagen fibril structure; (2) advanced glycation end product (AGE)-mediated crosslinking that occurs as a result of reaction of glycated proteins, including collagen, to non-enzymatically react with surrounding proteins; and (3) photooxidative CXL mediated by riboflavin as a treatment option for KC and corneal ectasia. Here, LOX is linked to keratoconus.