For example, decreased levels of cystatins SN, SA, and S (CST1, CST2, and CST4) and increased levels of transferrin (TF) and S100 calcium-binding protein A4 (S100A4) are frequently encountered in DE patients’ tear fluid [6], and thus indicate worsened ocular surface health among the medicated POAG patients as well. Here, S100A4 is linked to open-angle glaucoma.