NGF and glaucoma: Subgroups analysis showed that serum levels of NGF were significantly lower in early (3.5±0.9 pg/mL, p = 0.0008) and moderate glaucoma (3.8±0.7 pg/ml, p<0.0001) but not in advanced glaucoma (5.0±0.7 pg/ml, p = 0.32) compared to healthy controls.