Open-Angle Glaucoma

What is open-angle glaucoma?

Open-angle glaucoma (OAG) is the most common type of glaucoma— an eye disease that damages the optic nerve in your eye. In open-angle glaucoma, your eye’s drainage system starts to back up — usually, so slowly that you don’t notice. This prevents your eye fluids from draining normally. As fluids build up, they raise the pressure inside your eye, causing ocular hypertension. This damages your optic nerve.

OAG is a sneaky condition that starts without any obvious symptoms or causes and continues to worsen, causing gradual vision loss. You might not realize it’s happening until your vision is significantly impaired. This damage is irreversible. Treatment focuses on improving drainage and reducing the pressure in your eyes to stop the condition from progressing. Without treatment, OAG can progress to blindness.

How does open-angle glaucoma affect your vision?

Vision loss from open-angle glaucoma starts at the edges of your visual field (your peripheral vision) and slowly closes in on the center. Most people have vision loss in both eyes, but it’s usually more advanced in one eye. This makes it harder to notice, because the stronger eye compensates for the weaker one.

What are the symptoms of open-angle glaucoma?

Most people don’t notice symptoms until they have significant vision loss.

Signs might include:

• Missing a stair when walking downstairs
• Missing some of the letters in the word you’re reading
• Having trouble reading road signs while driving
• Having trouble seeing contrast in low light

You or your eye care provider may also notice specific visual field defects during testing, like:

• Nasal step defect: A blind spot on the side of your visual field close to your nose
• Arcuate scotoma: An arc-shaped blind spot on the top or bottom of your visual field
• Paracentral scotoma: A small, roundish blind spot just off the center of your visual field
• Temporal wedge defect: A wedge-shaped dark area on the temple side of your visual field

As OAG advances, it leads to gradually worsening tunnel vision.

How serious is open-angle glaucoma?

Open-angle glaucoma progresses slowly, but surely. It’s serious because it can affect your vision before you realize it. With treatment, you can stop or slow the progression. But without it, it can lead to low vision or blindness. Vision loss from OAG is usually painless. But some people develop a complication called retinal venous occlusion that causes eye pain with blindness. This can be more difficult to treat.

What causes open-angle glaucoma?

Your eyes have a built-in drainage system for the fluid that they produce. Glaucoma happens when something interferes with this drainage system and the fluid builds up inside. As this happens, it raises the pressure inside your eye. If your eye has elevated pressure for a long period of time, it can damage your optic nerve. This is the nerve that carries messages from your eye to your brain so you can “see.”

Sometimes, the problem in your eye’s drainage system is clearly visible, and sometimes it isn’t. In open-angle glaucoma, your eye’s drainage angle appears to be open and functioning normally. But somehow, resistance seems to build up within it. Experts believe the issue is in the trabecular meshwork — a spongy tissue inside the drainage angle that fluids drain through. Most treatments target this tissue.

Primary OAG vs. secondary OAG

The problem is similar to what happens to the trabecular meshwork with aging. It loses cells, changes form and becomes less functional. It’s almost like something has sped up the aging process in these tissues. Most of the time, there’s no obvious reason for this. In this case, healthcare providers call it primary open-angle glaucoma. But sometimes, another condition causes it, and then it’s called secondary open-angle glaucoma.

In secondary OAG, another condition clogs the pipes in your eye drainage system. Examples include swelling, protein deposits or cellular debris. Primary OAG is harder to explain. There’s often evidence of ocular hypertension, but not always. Sometimes, the pressure in your eye can still be normal, but you still have signs of damage to your optic nerve. Certain risk factors may increase your risk of primary OAG, including:

• Older age
• Biological family history of glaucoma
• African racial heritage

How is open-angle glaucoma diagnosed?

It’s tricky to get a glaucoma diagnosis if you don’t notice symptoms or vision changes. Seeing your eye care specialist for regular eye exams can help catch it sooner. If your provider has a record of your previous exams and your eye health history, they’ll be more likely to notice small changes and risk factors that could suggest glaucoma. This could lead to further testing and an earlier diagnosis.

Specialists diagnose OAG when you have evidence of:

• Visual field changes
• Optic nerve damage and/or high intraocular pressure (IOP)
• An open drainage angle

Tests to diagnose glaucoma may include:

• Visual field test
• Optical coherence tomography
• Gonioscopy
• Tonometry

What’s the best treatment for open-angle glaucoma?

Treatments for open-angle glaucoma include medications and procedures. Which treatment will work best for you will depend on your condition and how it responds. Most treatments aim to reduce the intraocular pressure (IOP) in your eye. Even if your IOP doesn’t seem especially high, studies show that reducing it slows the progression of glaucoma. This helps to preserve as much of your vision as possible.

Medications for OAG

Healthcare providers often start by prescribing medications to treat open-angle glaucoma. These are usually topical eye drops that either increase the outflow or decrease the production of the fluid building up in your eye. This reduces pressure. Don’t worry: this fluid (aqueous humor) is different from the tears that lubricate your eye. Adjusting these fluid levels won’t make your eyes too dry.

Common medications for OAG include:

• Prostaglandins. These synthetic hormones increase the outflow of your eye fluid through an alternative pathway. Examples include travoprost, bimatoprost and latanoprost.
• Beta-blockers. These medications, which commonly treat cardiovascular diseases, can also treat glaucoma by reducing eye fluid production. Examples include betaxolol and timolol.
• Rho-kinase inhibitors. ROCK inhibitors like netarsudil block the action of certain enzymes, causing the trabecular meshwork in your eye to relax and let more fluids through.
• Carbonic anhydrase inhibitors. These block the action of an enzyme involved in eye fluid production, reducing fluid production. Examples include brinzolamide and dorzolamide.
• Alpha-adrenergic agonists. These drugs stimulate certain nerve receptors in your eye to both decrease fluid production and increase outflow. They include brimonidine and apraclonidine.

Procedures for OAG

Your eye care provider might recommend eye surgery for OAG if medications aren’t helping enough, or you don’t want to continue using them. In some cases, they might recommend minimally invasive surgery as a frontline treatment to avoid medications. There are many types of glaucoma surgery. Procedures for open-angle glaucoma tend to focus on improving drainage in the trabecular meshwork.

Common procedures for OAG include:

• Laser trabeculoplasty. This eye surgery selectively targets parts of your trabecular meshwork with lasers. It provokes chemical changes in the tissue that allow fluid to drain from your eye.
• Goniotomy. This minimally invasive glaucoma surgery is performed in the operating room and removes the faulty/clogged trabecular meshwork, opening up the drainage system of the eye.
• Tube shunt surgery. This procedure implants a small device in your eye to drain fluid, bypassing the trabecular meshwork. When possible, surgeons use minimally invasive techniques.

Is open-angle glaucoma preventable?

Most of the time, there’s no obvious cause for open-angle glaucoma, so there’s no way to prevent it. But catching it and treating it earlier can prevent some of the damage it does. The best way to do this is to see your eye care provider regularly for routine eye exams. If you have a higher risk of developing OAG, your provider might recommend more frequent testing, or in some cases, preventive treatment.

What’s the prognosis for open-angle glaucoma?

With treatment, most people can stop OAG from progressing, or at least slow it down. But the vision loss you have before you start treatment is irreversible. Without noticeable symptoms, some people don’t realize they’re slowly losing their vision until it’s too late. While most people won’t progress to blindness, glaucoma is the second-leading cause of blindness worldwide. And most glaucoma is OAG.

For unclear reasons, glaucoma affects people with African racial heritage more severely than others. African American, Afro-Caribbean and West African people are four times more likely to develop it. They tend to develop it decades younger, and they’re six times more likely to be diagnosed with advanced vision loss. After cataracts, glaucoma (usually, OAG) is the leading cause of blindness in Black people.

How should I take care of myself while living with open-angle glaucoma?

If you’re treating OAG with medications, it’s important to take them consistently. Unlike procedures, medications aren’t a long-term fix for OAG. You have to take them every day, possibly forever. This may be difficult if they cause symptoms or side effects, or if you don’t notice the difference when you stop. If your current treatment plan isn’t working, be sure to revisit your options with your provider.