What Is Glaucoma?

How glaucoma affects a person's eyes

Glaucoma is the second-leading cause of blindness in the world, and it's six times more likely to occur in those over the age of 60. If someone close to you is diagnosed with glaucoma and it's left untreated, it could lead to tunnel vision or even blindness. Here's what you need to know about the disease and how to help the person cope.

Also know that early diagnosis and treatment can preserve a person's vision.

What's the cause of glaucoma?

If someone has glaucoma, it means that his optic nerve -- which carries images from the eye to the brain -- has been damaged. This is often the result of a buildup of fluid and pressure in the eye (known as intraocular pressure, or IOP), but scientists are also researching other causes, because people without elevated eye pressure also get glaucoma. Glaucoma can develop in both eyes or in only one eye. The more damage to the optic nerve, the more significant the vision loss.

The two main kinds of glaucoma

The first type is chronic, or open-angle, glaucoma, and the second type is acute, or angle-closure, glaucoma.

• Chronic glaucoma is the most common form, and it also advances more slowly and is easier to treat. It develops as the eye's drainage canals become clogged, resulting in a rise in inner eye pressure. It can cause a gradual, sometimes imperceptible, loss of sight over the course of years.
• Acute glaucoma results in a faster rise in eye pressure and more quickly advancing symptoms. In this case, the outer edge of the iris covers the drainage canals and blocks the fluid from draining. When this occurs, it's considered a medical emergency: The patient should see an eye doctor right away to prevent further vision loss. Signs that he may be having an acute glaucoma attack: severe eye pain (chronic glaucoma usually isn't painful), headaches, blurry vision, nausea, and vomiting.
• There's also a condition called secondary glaucoma, which means that something else (like another disease, a medication, or an injury) is causing increased eye pressure and damaging the optic nerve.

To see a picture of the eye and read about how eye drainage works, visit the Glaucoma Foundation's website.