text: Dry eye and delayed tear clearance: "a call to arms.".
  Dry eye may activate components of the ocular surface early warning system. Ocular surface stresses in dry eye, such as hyperosmolarity, could activate cellular stress pathways such as MAPKs. IL-1 and MMP-9 produced by the ocular surface epithelial cells may mediate initial events in the inflammatory cascade of dry eye through a dynamic interplay between them on the ocular surface.