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Glaucoma is the second-leading cause of blindness in the world, affecting around 70 million people globally. Primary open-angle glaucoma is the most common type of glaucoma.

In the United States, around 80 percent of people with glaucoma have primary open-angle glaucoma.

Primary open-angle glaucoma is a progressive condition, which means that if it’s not treated, it gets worse over time. The good news is that it can be detected through regular eye and vision screenings. Treatment can’t restore your eyesight, but it may slow the progression of the disease and prevent further vision loss.

This article will take a look at the causes, symptoms, and treatment of primary open-angle glaucoma and whether there are steps you can take to prevent it.

Primary open-angle glaucoma is an eye condition that causes gradual blindness. To understand how the disease affects your eyes and your eyesight, it’s important to take a look at two key functions that happen in a healthy eye.

1. Vision

  • Your eye is equipped with cells that act as light sensors, or photoreceptors. One type of photoreceptor is a retinal ganglion cell.
  • These cells are located in the retina, the structure at the back of the eye that gathers information about what you see.
  • The death of retinal ganglion cells is the underlying cause of blindness from glaucoma.
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2. Fluid balance

  • Your eye is filled with a liquid called aqueous humor. Its purpose is to keep your eye plump and to supply nutrients to the cells in your eye.
  • This fluid is continuously refreshed. As new aqueous humor is made, older fluid seeps out. There are two drainage pathways in your eye:
    • the trabecular meshwork (spongy tissue located near the cornea)
    • the uveoscleral outflow (a drainage route whereby aqueous humor seeps around, through, and between tissues that doesn’t involve the trabecular meshwork)
  • Both of these networks sit just behind your cornea near the front of your eye. When the older fluid doesn’t drain properly, pressure builds up inside the eye.
  • Too much intraocular pressure (pressure inside the eye) can damage the optic nerve and the cells that maintain your eyesight.
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Researchers have not yet pinpointed exactly what causes your eyes to stop draining properly. In some cases, the nerves that switch the draining process on and off don’t work well.

In other cases, tiny particles of pigment, blood cells, proteins, and other debris can block the trabecular meshwork drainage. Steroid therapies can also raise the pressure inside your eyes.

A 2020 research review showed that primary open-angle glaucoma occurs more frequently in:

  • adults more than 40 years old
  • Black people
  • people with a family history of glaucoma

Some health conditions can raise your risk of developing primary open-angle glaucoma. These include:

Using birth control pills, alcohol, and tobacco products can also increase your risk of developing primary open-angle glaucoma.

Closed-angle glaucoma means the iris (the colored ring) in your eye meets the cornea at an angle that blocks both the trabecular meshwork and the uveoscleral drainage systems.

Closed-angle glaucoma usually causes intense pain, nausea, and blurred vision. It often comes on suddenly, and is a medical emergency.

When the trabecular meshwork is blocked but the uveoscleral drain is open, glaucoma is said to be open-angle.

When glaucoma occurs without any underlying health condition (such as cataracts or an eye injury), the disease is said to be primary.

Primary open-angle glaucoma means the disease has developed without a known cause. Most cases of glaucoma are primary open-angle glaucoma.

When another health condition causes or contributes to the development of glaucoma, the disease is called secondary glaucoma. In other words, glaucoma has developed as a result of changes caused by the other health condition.

In the early stages, primary open-angle glaucoma doesn’t usually have any noticeable symptoms.

In advanced stages, it can cause blurred vision in one or both eyes, along with a narrowed field of vision.

With primary open-angle glaucoma, vision loss starts at the outer edges of your field of vision. As the disease progresses, your field of vision shrinks. If left untreated, primary open-angle glaucoma can cause blindness.

An ophthalmologist or an optometrist can test your eyes for glaucoma as part of a routine eye exam. There are several different types of tests that your eye doctor can use to check for signs of glaucoma.

  • Tonometry. This test measures the pressure inside your eye. After numbing your eye with eye drops, your doctor will use a small device called a tonometer to measure the inner pressure of your eyes.
  • Ophthalmoscopy. Your doctor or a technician will give you eye drops to dilate your pupil — this is the opening at the front of your eye that lets in light. Once your eye is dilated, your eye doctor will use a device with a light on the end to examine your optic nerve.
  • Visual field test. This test involves covering one eye at a time and then looking straight ahead while lights flash in your peripheral vision. The purpose of this test is to determine whether you have any loss to your peripheral vision.
  • Pachymetry. With this quick, painless test, your doctor will gently place a probe on the front of your eye to measure the thickness of your cornea. This test is done because corneal thickness can, in some instances, influence eye pressure readings.
  • Gonioscopy. After numbing your eye with drops, your doctor will place a hand-held contact lens on your eye to determine whether the angle where the iris meets the cornea is open or closed.

The goal of primary open-angle glaucoma treatment is to lower the pressure in your eye to prevent any further damage or vision loss. Treatments vary according to how advanced your glaucoma is and what’s possibly causing the problem.


The National Eye Institute says that the first-line treatment for primary open-angle glaucoma is usually prescription eye drops. One of the most common types of eye drops to help treat this condition are prostaglandins.

Prostaglandins are fatty acids that can help improve drainage inside your eye. These drops are taken before bed every night. Some of the most commonly prescribed prostaglandins for primary open-angle glaucoma include:

Some other types of eye drops can help lower the amount of fluid your eye produces. These medications include:

  • beta-blockers
  • alpha-adrenergic agonists
  • carbonic anhydrase inhibitors

Glaucoma eye drops are usually safe for most people. However, there’s a small possibility of side effects such as:

  • changes to the color of your iris
  • stinging and redness in your eye
  • blurry vision
  • dry mouth

Laser treatment

If eye drop medications don’t lower your eye pressure enough, your eye doctor may recommend a type of laser procedure called selective laser trabeculoplasty (SLT). Some new research has shown that SLT may be as effective as eye drops in early glaucoma.

This in-office procedure only takes a few minutes and involves your eye doctor aiming a laser at the drainage tissue in your eye.

The laser energy causes a chemical change in the eye tissue that can result in better drainage of fluid inside your eye. This, in turn, may help lower the pressure inside your eye by 20 to 30 percent, according to the Glaucoma Research Foundation. This procedure is successful in around 80 percent of cases, and the effects typically last between 3 to 5 years.

Your eye will be numbed during the laser treatment, but there can be some tenderness, redness, or dryness afterward. Your doctor may prescribe some eye drops to help your eye heal.


Several types of surgery can be done to encourage better drainage. This includes:

  • minimally invasive glaucoma surgery, which involves a surgeon using microscopic tubes to drain fluid from the eye
  • trabeculectomy, in which the surgeon opens a tiny hole in the surface of your eye to allow fluid to escape
  • glaucoma implant surgery, where surgeons place a small tube called a shunt into your eye to help fluid drain properly

Some people of certain ages, races, or family histories develop primary open-angle glaucoma more frequently, which can result in the eye changes that cause glaucoma. If you’re concerned about developing this condition, your doctor can work with you to help you manage your overall eye health as much as possible.

If you have a health condition that raises your risk of developing primary open-angle glaucoma, it’s important to manage that condition well. And if you smoke, use alcohol, or take birth control pills, you may want to talk with a healthcare professional about ways to reduce the risk of glaucoma.

The most important preventative step you can take is to have regular eye exams. Because symptoms do not appear until later in the course of this disease, it’s important to detect glaucoma early to prevent vision loss.

Primary open-angle glaucoma is a progressive condition that can cause permanent vision loss, and even blindness, if left untreated. It happens when retinal ganglion cells are damaged, causing the gradual loss of peripheral, and then central vision.

Primary open-angle glaucoma is caused by too much pressure within the eye. When fluid does not drain properly, the excess pressure can harm the optic nerve.

Primary open-angle glaucoma does not cause vision loss or other symptoms until later stages. For that reason, it’s important to have regular eye exams. Your eye doctor can test the pressure in your eye and evaluate your field of vision to detect glaucoma in its earliest stage, before it affects your vision.