Glaucoma occurs when an excess of ocular (eye) fluid does not drain properly, causing damage to the optic nerve and resulting in blurred vision, a narrowed field of vision with some loss of peripheral vision, and eventually total blindness.
The three main types of glaucoma are:
- Open-angle glaucoma. This is the most common form, also called primary open-angle glaucoma. In open-angle glaucoma, the trabecular meshwork, a spongy tissue near the cornea and iris that drains ocular fluid, slowly becomes less effective at doing its job. When this occurs, intraocular pressure (IOP), rises to dangerous levels. This condition is almost always asymptomatic in the early stages. Thus, the patient is often unaware of the developing condition.
- Normal-tension glaucoma. In normal-tension glaucoma, damage occurs to the optic nerve despite an IOP within the normal range, between 10-20 millimeters of mercury (mm Hg).
- Closed-angle glaucoma, also called narrow-angle glaucoma or angle-closure glaucoma. This less common form of glaucoma happens suddenly, when the iris (colored part of the eye) shifts positions and blocks the flow of fluid through a drainage channel called the drainage angle. This can cause IOP to raise rapidly, necessitating emergency response, which may include emergent surgery.
Glaucoma affects more than 60.5 million people worldwide, a number that is expected to grow as the global population ages. Glaucoma is a leading cause of blindness in the US, and costs the U.S. economy around $2.86 billion each year in health care expenditures and lost productivity.