What is glaucoma?

Glaucoma is a disease of the optic nerve, the part of the eye that carries the images we see to the brain. The optic nerve is made up of many nerve fibers, like an electric cable containing numerous wires. When damage to the optic nerve fibers occurs, blind spots develop. These blind spots usually go undetected until the optic nerve is significantly damaged. If the entire nerve is destroyed, blindness results.

Glaucoma is the leading cause of blindness in the United States, especially for older people. But loss of sight from glaucoma can often be prevented with early treatment.

What causes glaucoma?

Clear liquid called aqueous humor circulates inside the front portion of the eye. To maintain a healthy level of pressure within the eye, a small amount of this fluid is produced constantly while an equal amount flows out of the eye through a microscopic drainage system.

Because the eye is a closed structure, if the drainage area for the aqueous humor (called the drainage angle) is blocked, the excess fluid cannot flow out of the eye. Fluid pressure within the eye increases, pushing against the optic nerve and causing damage.

What are the different types of glaucoma?

The most common form is chronic open-angle glaucoma and the risk of developing this form increases with age. The drainage angle of the eye becomes less efficient over time, and pressure within gradually increases, which can damage the optic nerve. Typically open-angle glaucoma has no symptoms in its early stages. As the optic nerve becomes more damaged, blank spots appear in the field of vision.

You typically won’t notice these blank spots until the optic nerve is significantly damaged and these spots become large. If all the optic nerve fibers die, blindness results. Closed-angle glaucoma occurs in people whose eyes are formed with the iris (the colored part of the eye) too close to the drainage angle. In these eyes, the iris can be sucked into the drainage angle and block it completely. Since the fluid cannot exit the eye, pressure inside builds rapidly and causes acute closed-angle attack. This is a true eye emergency and unless this type of glaucoma is treated quickly, blindness can result.

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