The result showed that PA and Dex greatly suppressed MMP9 level in inflammatory cell model while increased Col I expression Therefore, it is reasonable to suggest that using corticosteroids, especially PA and Dex, at the early stage of keratitis could maintain the main collagen component, Col I and Col VI, expression in stroma and reduced its degradation while decreasing MMP9 expression. Here, MMP9 is linked to keratitis.