SFRP1 and open-angle glaucoma: When we evaluated the relationship between IOP and AH levels of SFRP1, we unexpectedly found a statistically significant, negative correlation between the SFRP1 level and IOP in the POAG group (P = 0.011) (Fig. 4b), while no significant (P > 0.05) correlation was observed between IOP and AH concentration of SFRP1 in cataract, PACS, AACG or CACG group (Fig. 4a, c, d, e).