MMP9 and graft versus host disease: GVHD group was characterized by positive correlations between MMP-9 and conjunctival staining (rho = 0.55, p=0.0002) and between MMP-9 and OSDI (rho = 0.3, p=0.01); a faint inverse correlation was found between MMP-9 and Schirmer test (rho = −0.25, p=0.04).