MMP9 and keratoconus: Therefore our aim was to determine and to compare the concentrations of various mediators (IL-6, -10, CCL5/RANTES, CXCL8/IL-8, chemokine (C-X-C motif) ligand (CXCL10)/interferon-gamma-inducible protein 10 (IP-10), MMP-9, -13, TIMP-1, tissue plasminogen activator (t-PA), plasminogen activator inhibitor (PAI-1) and NGF) in the tear film of patients with PMD and KC in order to reveal any possible biochemical differences between these two entities.