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Maintenance and repair of corneal stromal extracellular matrix (ECM) requires a tightly coordinated balance of ECM synthesis, degradation and remodeling in which proteolytic enzymes (proteinases) perform important functions. There are natural proteinase inhibitors present in preocular tear film (PTF) and cornea simultaneously with proteinases that prevent excessive degradation of normal healthy tissue. Disorders occur when there is an imbalance between proteinases and proteinase inhibitors in favor of the proteinases, causing pathologic degradation of stromal collagen and proteoglycans in the cornea. Two matrix metalloproteinases (MMPs), MMP‐2 and MMP‐9, are of major importance in terms of remodeling and degradation of the corneal stromal collagen. Immunohistochemical studies have shown different origins of MMP‐2 and ‐9. MMP‐2 is synthesized by corneal keratocytes and performs a surveillance …