Acute Glaucoma.

Acute glaucoma is a less common (but very serious) form of glaucoma. It is characterized by increased eye pressure, intense pain, and rapid damage to the optic nerve. Without immediate treatment during an attack, this condition can quickly lead to vision loss. People who have farsightedness, diabetes, or a family history of glaucoma are at a higher risk of developing it.
What Is Acute Glaucoma?
Acute glaucoma is one of the many different glaucoma types (see Types of Glaucoma). It is much less common than chronic glaucoma (also known as open angle glaucoma). However, acute glaucoma is very serious because it can cause rapid damage and loss of vision; it can also erupt in violent attacks and intense pain, rather than emerging subtly.

This condition occurs in less than 10 percent of glaucoma cases.
Other names for acute glaucoma include:
•Closed angle glaucoma
•Angle closure glaucoma
•Narrow angle glaucoma.

How Acute Glaucoma Affects the Eye
The cornea is the clear outer covering of the eye. Separating it from the iris (the colored part) is the anterior chamber, a space filled and inflated by aqueous humor. This clear fluid (unrelated to the tears that bathe the outside surface of the cornea) starts in the ciliary body just behind the iris. It circulates in the anterior chamber, nourishing the eye's delicate tissue and keeping it from collapsing.

To maintain equilibrium, the aqueous humor drains through a porous tissue in the angle in front of the iris, where it meets the cornea, called the trabecular meshwork.

If the aqueous humor cannot drain properly because the iris is pushing against the cornea (as in acute glaucoma), it backs up, putting pressure on the gel in the vitreous cavity at the center of the eye. Eventually, the building pressure affects the delicate optic nerve at the rear of the eye. Since the optic nerve transmits visual images to the brain, any damage to it reduces vision.

The optic nerve is a bundle of more than one million nerve fibers. It connects the retina to the brain. The retina is the light-sensitive tissue at the back of the eye. A healthy optic nerve is necessary for good vision.