FN1 and glaucoma: In terms of the mechanism responsible for the increase in IOP, elevated resistance to AH outflow from the TM caused by the excess deposition of extracellular matrix (ECM) such as collagens (COLs), fibronectin (FN) and others is primarily thought to be responsible for the development of both primary open angle glaucoma (POAG) and steroid-induced glaucoma (SG)6.