Glaucoma is an eye disease that most often causes elevated intraocular pressure, which when left undiagnosed or untreated can cause damage to the optic nerve, in turn, leading to loss of vision and eventually, blindness.
There are several types of glaucoma. The two main types are open-angle and angle-closure. These are marked by an increase of intraocular pressure (IOP) or pressure inside the eye.
Open-angle glaucoma, the most common form of glaucoma, accounting for at least 90% of all glaucoma cases:
Is caused by the slow clogging of the drainage canals, resulting in increased eye pressure
Has a wide and open angle between the iris and cornea
Develops slowly and is a lifelong condition
Has symptoms and damage that are not noticed.
“Open-angle” means that the angle where the iris meets the cornea is as wide and open as it should be. Open-angle glaucoma is also called primary or chronic glaucoma. It is the most common type of glaucoma, affecting about three million Americans.
Angle-closure glaucoma, a less common form of glaucoma:
Is caused by blocked drainage canals, resulting in a sudden rise in intraocular pressure
Has a closed or narrow-angle between the iris and cornea
Develops very quickly
Has symptoms and damage that are usually very noticeable
Demands immediate medical attention.
It is also called acute glaucoma or narrow-angle glaucoma. Unlike open-angle glaucoma, angle-closure glaucoma is a result of the angle between the iris and cornea closing.
Normal-Tension Glaucoma (NTG)
Also called low-tension or normal-pressure glaucoma. In normal-tension glaucoma, the optic nerve is damaged even though the eye pressure is not very high. We still don’t know why some people’s optic nerves are damaged even though they have almost normal pressure levels.
This type of glaucoma occurs in babies when there is an incorrect or incomplete development of the eye’s drainage canals during the prenatal period. This is a rare condition that may be inherited. When uncomplicated, microsurgery can often correct the structural defects. Other cases are treated with medication and surgery.
Other Types of Glaucoma
Variants of open-angle and angle-closure glaucoma include:
Irido Corneal Endothelial Syndrome (ICE)
Source: Glaucoma Research Foundation