Within this context, the objectives of this study were: a) to trace and estimate the levels of TIMP4 in the aqueous humor, b) to investigate the ratios of TIMP4 to other free MMPs and TIMPs in the aqueous humor, and c) to investigate the potential imbalance of free forms of MMPs and TIMPs in eyes with POAG, PXS and PXG. This evidence concerns the gene TIMP4 and open-angle glaucoma.