Is Normal Tension Glaucoma Different Than High Tension Glaucoma

Primary open-angle glaucoma (POAG) is a progressive optic neuropathy that is often arbitrarily stratified by the intraocular pressure (IOP) level associated with initial damage into high-tension glaucoma (HTG) and normal- tension glaucoma (NTG) subtypes. Patients with both POAG subtypes exhibit a variety of ocular and non-ocular vascular abnormalities and there is no evidence these abnormalities predominate in one subtype or the other. Interestingly common genetic variation in NOS3 and the CAV1/CAV2 genomic regions, which code for proteins involved in setting vascular tone, are associated with POAG but these markers seem to stratify with POAG subtypes by sex or pattern of initial visual field loss. Overall it is clear that there is also cardiovascular autonomic dysfunction in HTG and NTG but it is unclear if this dysfunction is more common in NTG compared to HTG.