Glaucoma: What Are the Basics?

Glaucoma is a collection of diseases linked by a common outcome: irreversible damage to delicate nerve fibers and the optic nerve that sends information to the brain. It’s often called "the silent thief of sight," because major, irreversible damage can take place before you know you have it.

It works like this: All day long, your eye makes and drains away a fluid called aqueous humor. As new batches are made, an equal amount of liquid must exit through a passageway called the trabecular meshwork. Glaucoma backs up that drainage system, and your eye pressure rises. If the pressure stays high to long (we’re talking years), it can damage your retinal and your optic nerve fibers.

More than 3 million adult Americans have glaucoma. This makes it one of the leading causes of blindness in the U.S.

What Are the Different Types?

Chronic open-angle glaucoma is the most common type of glaucoma outside of Asia. It accounts for about 75%-90% of cases. This type has multiple causes, but doctors think it may be genetic: One in five people with it has a close relative who also has it. It can affect both eyes at the same time, but one may be worse than the other.

This form generally shows up in middle age. It takes your sight away in stages. Your vision will first begin to fade in the outer edges (your doctor will call this peripheral vision). If you don’t treat it, it’ll narrow down to tunnel vision and then blindness.

Narrow or closed-angle glaucoma is less common and may come on fast. It usually affects one eye first. You’ll notice blurred vision, pain in your eye and head, and redness. It completely blocks the outflow of liquid. That can cause a sudden and severe rise in pressure inside your eye. And just like in open-angle glaucoma, the high pressure permanently damages your nerves.

This form is a medical emergency. You need medical care right away to drain the liquid, ease eye pressure, and prevent permanent damage or even blindness. It, too, can slowly and silently damage your nerves. This type is more common in Asia. In certain countries, it’s the more common form of glaucoma.


Congenital glaucoma is rare. Some infants have it at birth or get it within the first few years of life. You’ll notice that your child’s corneas (the front of his eye) are cloudy and that his eyes are sensitive to light and tear up all the time. If the problem isn’t diagnosed and treated early, he could lose some or all of his vision. There’s a similar type that shows up between age 3 and adulthood. It’s called juvenile glaucoma.

Secondary glaucoma is a broad category of problems usually linked to another eye disease or disorder, like a very mature cataract, inflammation inside your eye (the doctor will call this uveitis), bleeding, eye tumor, or a previous eye injury. If you have diabetes, extra blood vessels can form inside your eye and block the outflow of fluid. This severe form of the disease is called neovascular glaucoma.

WebMD Medical Reference Reviewed by Alan Kozarsky, MD on March 07, 2015



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