EDN1 and glaucoma: Furthermore, elevated plasma ET-1 level of glaucoma patients correlated significantly positively with age (p = 0.035; Table 2), refraction (p = 0.031; Table 2), vertical CDR (p = 0.044; Table 2) and disc area (p < 0.01; Table 2) and significantly negatively with IOP (p = 0.030; Table 2).