Matrix metalloproteinase-9 in the pathophysiology and diagnosis of dry eye syndrome

Dry eye and tear dysfunction are common ocular disorders that cause cornea barrier disruption resulting in a poorly lubricated and irregular cornea epithelium, eye irritation and blurred vision. Increased levels and activities of matrix metalloproteinases (MMPs), particularly MMP-9, have been detected in the tears and ocular surface epithelial and inflammatory cells in dry eye. MMPs have been found to participate in disruption of tight junctions in the apical cornea epithelium leading to their accelerated desquamation and barrier disruption. This review summarizes evidence showing the contribution of MMPs to dry eye pathogenesis and their roles as biomarkers and therapeutic targets.