Abstract: Normal tension glaucoma (NTG) has been considered as a subtype of primary openangle glaucoma (POAG) since it has lots of common clinical features with the latter except the normal intraocular pressure (IOP). However, its risk factors were found to be different from those of hightension openangle glaucoma according to the gradual deepening  awareness of the disease. Systemic and local factors both have an impact on the development of NTG. We discuss the risk factors including sex, age, cerebral ischemia, IOP fluctuation, axial length and refractive error respectively in this review.