MMP9 and dry eye syndrome: For example, levels and activity of MMP-9 in the tear film have been shown to be elevated in patients with dry eye disease, and studies of experimentally induced dry eye in MMP-9 knockout and wild-type mice have demonstrated that MMP-9 participates in the destruction of the corneal epithelium caused by dry eye.15 Studies using MMP-2 and MMP-9 knockout and wild-type mice have further implicated both MMP-2 and MMP-9 in the development of choroidal neovascularization induced by laser-induced rupture of Bruch's membrane in a mouse model of neovascular age-related macular degeneration.16