Glaucoma refers to a group of progressive eye diseases that cause vision loss by damaging the optic nerve in the back of the eye. The optic nerve is a bundle of more than 1 million nerve fibers that carry messages from the retina, where light is converted into nerve impulses to the brain. The brain interprets the impulses as visual images.

January is National Glaucoma Awareness Month. Let’s learn more about glaucoma, which affects about 3 million Americans and 80 million people worldwide. It is the second leading cause of blindness in the world, behind cataracts.

One of the main risk factors for glaucoma is increased pressure in the eyes, or intraocular pressure (IOP). High IOP damages optic nerve fibers, leading to vision loss. IOP increases when the fluid that bathes and nourishes the front of the eye, called aqueous humor, cannot drain as fast as it is created and builds up.

Fluid drains through an area called the drainage angle, located where the colored part of the eye (iris) meets the white covering over the eye (sclera). One of the main structures of the drainage angle is the trabecular meshwork, which plays an important role in draining aqueous humor from the eye and maintaining a consistent IOP.

In addition to high IOP, other risk factors for glaucoma include being older (it is more common in people ages 60 and older), being African American or Latino, having a family history of glaucoma, having diabetes (people with diabetes are twice as likely to develop glaucoma), being very nearsighted or farsighted, using corticosteroids long-term and having a thin cornea.

Anyone with a risk factor should see an eye doctor for an annual exam.

There are two main types of glaucoma:

• Open-angle glaucoma is the most common, affecting up to 90 percent of Americans with glaucoma. It develops when tiny deposits build up in the eye’s drainage canals and slowly clogs them so fluid cannot drain efficiently. It typically has no symptoms early on. As the disease progresses, peripheral (side) vision may diminish. Because the disease can get to that point without symptoms, it is often called the “silent thief of sight.”

• Angle-closure glaucoma occurs when the iris is too close to the eye’s drainage angle. It can block the drainage angle so fluid cannot drain and IOP increases. If the angle gets completely blocked, IOP increases rapidly and causes symptoms. This is called acute angle-closure glaucoma. Signs of an attack include sudden blurry vision, severe eye pain, eye redness, headache, nausea, vomiting and rainbow-colored halos around lights.

Acute angle-closure glaucoma is a medical emergency. Anyone experiencing one of these symptoms should seek help immediately.

Because it causes no symptoms early on, it is possible to have glaucoma and not know it. So, routine eye exams are important to catch glaucoma before it can severely damage the optic nerve.

A doctor may perform one or more tests to check for glaucoma. These include a dilated eye exam to view the optic nerve, a gonioscopy to examine the drainage angle, tonometry to measure IOP, optical coherence tomography (OTC) to look for changes in the optic nerve that may indicate glaucoma, a visual acuity test (eye chart test) to check for vision loss and a visual field test to check peripheral vision.

If you have glaucoma, it is important to start treatment right away. A person cannot regain any vision already lost, but treatment can help slow the progression of the disease and reduce the risk of additional vision loss. To treat glaucoma, doctors typically use medications, laser procedures or surgery.

The most common medications for glaucoma are prescription eyedrops. These work by decreasing the production of aqueous humor or increasing its flow out of the eye. More than one eyedrop may be prescribed to control IOP.

The doctor may use a laser to help fluid drain from the eye. Lasers can be used to treat open-angle and angle-closure glaucoma. A laser can open the drainage angle, make a tiny hole in the iris to let the fluid flow more freely and treat areas in the eye’s middle layer to lower fluid production.

If eyedrops and laser treatments don’t lower IOP, the doctor may suggest surgery. There are several procedures that can help drain the fluid, including trabeculectomy microsurgery, in which the doctor creates a new drainage channel.

Minimally invasive glaucoma surgery (MIGS) makes tiny openings in the trabecular meshwork and places tiny devices, such as stents and microshunts, to help drain fluid. MIGS is most often performed as an add-on procedure after cataract surgery.

Now that you’ve had a glimpse at glaucoma, share what you’ve learned this National Glaucoma Awareness Month.

Patti DiPanfilo

Glaucoma is a group of progressive diseases that can damage your eye’s optic nerve and cause vision loss, even blindness. There are many theories, but the exact cause of glaucoma is unknown. It is most often related to a build-up of pressure inside your eye. When this pressure, called intraocular pressure, or IOP, remains high over time, it begins to harm optic nerve fibers.

IOP increases when the fluid inside your eye, called aqueous humor, which normally flows out of your eye through a mesh-like drainage channel called the trabecular meshwork, gets blocked and cannot leave the eye. As a result, the fluid builds up and IOP increases. In some case, however, glaucoma can occur in people who have normal IOP.

Another theory suggests that glaucoma is caused by an inadequate amount of blood flow to the optic nerve.

About 3 million Americans have glaucoma. It’s expensive and damaging to vision. It costs the US economy $286 billion every year in direct costs and productivity loses, and it’s the leading cause of irreversible blindness in the world.

There are two main types of glaucoma: open-angle glaucoma and angle-closure glaucoma.

Open angle glaucoma is the most common type, affecting approximately 95 percent of patients. In this type of glaucoma, fluid does not drain properly due to changes in and along the drainage passageway. There are typically no early symptoms of open-angle glaucoma, so you can have it for years and not know it. It is often called “the silent thief of sight.”

With angle-closure glaucoma, your eye doesn’t drain like it’s supposed to because the drain space, or angle, which is located between your iris and cornea, becomes too narrow and can become blocked. This can occur suddenly, which is called acute angle-closure glaucoma, or over time, called chronic angle-closure glaucoma.

Anyone can develop glaucoma, but there are certain factors that increase your risk for developing it. You are more likely to get it if you are over age 40, have a family history of glaucoma, have diabetes, take certain steroid medications such as prednisone, have had an injury to your eyes, have high eye pressure, or are nearsighted or farsighted. There are other risk factors as well.

Glaucoma-related damage to the optic nerve generally starts with a loss of nerve tissue in a specific pattern called cupping. This is when the center of the optic disc, called the cup, becomes larger, leaving less room for the remaining optic nerve fibers. It’s common for you to experience blurry spots in your peripheral, or side, vision when this occurs. This is often the first symptom of glaucoma.

As your glaucoma progresses, it may begin to affect your central vision, which is needed to see details and for activities such as driving and reading. Advanced glaucoma can lead to permanent blurred or dimmed vision or even to blindness.

Your eye doctor may use several painless tests to diagnose glaucoma in addition to a dilated eye exam and visual field test. Tonometry measures eye pressure; gonioscopy examines the drainage area of the eye, and optical coherence tomography (OCT) creates a three-dimensional image of the optic nerve and retina to evaluate the degree of cupping and ocular damage.

Glaucoma is treated using medications, laser therapy, and surgery. Medications, which may include eye drops or pills, lower eye pressure by reducing the amount of aqueous humor produced in the eye. They also help increase the outflow of fluid from the eye..

A laser procedure called trabeculoplasty opens clogs in the trabecular meshwork so fluid can drain out of the eye. Laser iridotomy, which is used for angle-closure glaucoma, creates a tiny opening in the iris to allow the drainage angle to open.

During a glaucoma surgery called trabeculectomy, the doctor creates a new channel in your eye to allow the fluid to drain, which eases IOP. Another surgical procedure your doctor may choose involves implanting a tube to help drain fluid from your eye.

Glaucoma treatment cannot restore vision you may have already lost, but it can help prevent any further vision loss.

Because glaucoma has no early symptoms, people at high risk should see their eye doctor for a dilated eye exam and visual field test at least every one to two years or as directed by their doctor. Don’t let glaucoma steal your sight. See your eye doctor today!