Glaucoma ducts, and narrowing or closure of the angle between the iris and cornea. The primary division in categorizing different types of glaucoma is open-angle and closed-angle (or angle-closure) glaucoma. In open angle glaucoma, the iris meets the cornea normally, allowing the fluid from inside the eye to drain, thus relieving the internal pressure. Where this angle is narrowed or closed, pressure increases over time, causing damage to the optic nerve, leading to blindness. Primary open-angle glaucoma (also, "primary glaucoma", "chronic glaucoma") refers to slow clogging of the drainage canals resulting in increased eye pressure which causes progressive optic nerve damage.
Normal tension glaucoma nerve head, in the absence of elevated IOP. While the excavation of the optic nerve head and the thinning of its rim appear in all kinds of glaucoma (with high tension and with normal tension,in Primary open angle glaucoma (POAG) and in secondary glaucoma), small hemorrhages close to the optic disc have been identified as a characteristic clinical sign of normal tension glaucoma. Visual field is very important to detect NTG. It shows a defect that typically appear deeper, steeper and closer to fixation comparing to patients with POAG. Since NTG is closely linked to vascular irregularities, a medical check-up