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.

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.

Variants of open-angle and angle-closure glaucoma include:

Secondary Glaucoma

Pigmentary Glaucoma

Pseudoexfoliative Glaucoma

Traumatic Glaucoma

Neovascular Glaucoma

Irido Corneal Endothelial Syndrome (ICE)

Uveitic Glaucoma

Source: Glaucoma Research Foundation