MMP9 and glaucoma: In this context, by employing animal models related to glaucoma, such as retinal ischemia [16] and excitotoxicity [17], [18], [19], we have previously reported that astrocytes become reactive, synthesize elevated levels of matrix metalloproteinase-9 (MMP-9) and urokinase plasminogen activator (uPA), and promote the death of RGCs by degrading extracellular matrix present in the ganglion cell layer [16], [19].