MMP2 and myopia: For example, matrix metalloproteinase-2 (MMP-2) is a scleral extracellular matrix degradation enzyme, and its activation induces collagen fiber I degradation, followed by loss of scleral connective tissue, together with scleral thinning and weakening, which leads to axial elongation and myopia (Ikeda et al. 2020; Lin et al. 2016).