Other inflammatory mediators, such as IL-6, TNF-α, and MMP-9, are increased both in the tears and the serum of patients with KC [85,86,87,88,89]; elevated concentrations of interleukin-8 (IL-8) were found both in corneal cells and blood samples from patients with KC [90]; and an increased neutrophil-to-lymphocyte ratio (a marker of systemic inflammation) was found to be associated with progressive KC, once again prompting the suggestion that KC may be part of a systemic inflammatory disorder [91]. Here, MMP9 is linked to keratoconus.