Open-Angle Glaucoma: Symptoms, Causes & Treatment

What is Open-Angle Glaucoma?

Primary open-angle glaucoma is a progressive eye disease caused by increased intraocular eye pressure (IOP). It leads to optic nerve (connection pathway between the eye and brain) damage and vision loss. If left untreated, open-angle glaucoma results in blindness.

Glaucoma is an umbrella term for eye conditions caused by increased eye pressure. The eye is filled with aqueous humor (clear fluid) that is responsible for eye shape and providing the rest of the eye with nutrients and oxygen. 

Eye fluid continuously flows, draining through a small space between the iris (colored part of the eye) and sclera (white of the eye) called the drainage angle. When the drainage angle is blocked or clogged, it leads to increased IOP. This causes damage to the optic nerve, leading to glaucoma.

Open-angle glaucoma is the most common type of glaucoma. It affects 3 million Americans and is the second leading cause of blindness worldwide.¹

Open-Angle vs. Closed-Angle Glaucoma

Glaucoma results from the drainage angle becoming blocked or clogged. This slows down the flow of eye fluid and increases eye pressure.

With primary open-angle glaucoma, the trabecular meshwork (spongy tissue in the drainage angle) slowly becomes clogged. This results in a backup of eye fluid, causing eye pressure to increase.

Closed-angle glaucoma, also called angle-closure glaucoma, is a sudden spike in intraocular pressure caused by the iris blocking the drainage angle. 

Symptoms of closed-angle glaucoma include:

• Sudden blurred vision
• Severe eye pain
• Headache
• Nausea and/or vomiting
• Rainbow halos around light 

Closed-angle glaucoma is a medical emergency that requires immediate treatment before it causes irreversible blindness.

Other Types of Glaucoma

A variety of eye conditions that increase intraocular pressure can cause glaucoma.

Other types of glaucoma include:

• Normal-tension glaucoma (optic nerve damage without a rise in IOP)
• Secondary glaucoma (caused by medical conditions, eye injury, or medications)
• Pigmentary glaucoma (flakes of pigment block drainage system)
• Congenital glaucoma (high eye pressure at birth)
• Exfoliative glaucoma (flaky material falls off into the trabecular meshwork, causing elevated IOP)
• Uveitic glaucoma (inflammation of the iris)
• Traumatic glaucoma (caused by eye injury or blunt force trauma)

Open-Angle Glaucoma Symptoms

Open-angle glaucoma progresses slowly over time. It is usually asymptomatic until its advanced stages, when the optic nerve is damaged. 

It is called the “silent thief of sight” because many people don’t know they have increased eye pressure until their peripheral vision (side vision) changes. 

Late-stage symptoms of open-angle glaucoma include:

• Blurred vision
• Blind spots in central vision
• Decreased color vision
• Reduced night vision

Causes of Open-Angle Glaucoma

Open-angle glaucoma is caused by increased intraocular pressure. This results in optic nerve damage, which causes vision loss.

The drainage angle stays open, but the trabecular meshwork becomes clogged. This slows down the flow of eye fluid and increases eye pressure. 

Risk Factors for Open-Angle Glaucoma

While anyone can develop glaucoma, certain people have increased risk factors, including:

• People over age 40
• A family history of glaucoma
• Severe nearsightedness and farsightedness
• Of African, Hispanic, or Asian descent
• History of eye injury
• Thinning of the cornea
• Diabetes
• Migraines
• High blood pressure
• Long-term steroid use

Can You Prevent Open-Angle Glaucoma?

There is no cure for glaucoma, and optic nerve damage is permanent. However, there are steps you can take to detect glaucoma early and manage eye health, including:

• Get a routine comprehensive eye exam from a licensed eye doctor
• Wear eye protection
• Control blood pressure and blood sugar
• Know your family history
• Take prescribed daily eye drops for high eye pressure

When to See an Eye Doctor

Visit an eye doctor right away If you experience vision changes or other symptoms of glaucoma, including:

• Sudden vision loss 
• Severe eye pain
• Headache
• Difficulty focusing
• Blind spots in your peripheral (side) or central 

Routine eye exams are essential if you are at high risk of developing glaucoma.

How is Open-Angle Glaucoma Diagnosed?

A licensed ophthalmologist can diagnose open-angle glaucoma during a comprehensive eye exam. During the exam, the eye doctor will measure intraocular pressure using a tonometry test or a “eye puff” test.

They will use special eye drops to dilate your eyes to examine the retina (layer in the back of the eye that sends light messages to the brain), optic nerve, and other eye structures for signs of disease.

Other eye tests that can help diagnose or monitor glaucoma include:

• Visual field test of the side and central vision
• Optical coherence tomography images your optic nerve to check for damage
• Visual acuity test to examine clarity and distance vision
• Measure corneal thickness

Open-Angle Glaucoma Treatment Options

Glaucoma can’t be cured or reversed. However, there are effective treatment options that help slow its progression and preserve vision.

The first goal of treating open-angle glaucoma is reducing intraocular pressure to minimize optic nerve damage. Treatment options include medication, laser therapy, and surgery. 

Medication

Medicated eye drops can control eye pressure. You will most likely need to administer daily eye drops for the rest of your life. In some cases, laser or surgery can reduce the need for drops.

Prescribed eye drops for glaucoma include:

• Beta-blockers to reduce eye fluid production
• Prostaglandins to increase outflow
• Alpha-adrenergic agonists to reduce eye fluid production and increase outflow
• Miotic or cholinergic agents to increase eye fluid outflow

Laser Therapy

If medication alone does not lower eye pressure, laser surgery can repair the drainage angle and restore the continuous flow of eye fluid.

Trabeculoplasty is laser surgery that treats open-angle glaucoma. It unclogs the drainage angle, allowing eye fluid to flow continuously, and decreasing eye pressure. 

Glaucoma Surgery

Traditional glaucoma surgery is used when medication is ineffective in reducing intraocular pressure. Glaucoma surgery aims to repair the drainage system and unclog the trabecular meshwork.

Types of glaucoma surgery used to treat open-angle glaucoma include:

• Trabeculectomy, which creates a tiny flap in the sclera and drainage reservoir for eye fluid
• Glaucoma drainage device, which is a small implanted tube used to drain eye fluid 
• Cataract surgery, which implants an artificial lens to correct narrow angles 

Outlook

While glaucoma is irreversible, it can be treated to slow disease progression and minimize vision loss.

Catching open-angle glaucoma in its early stages is the best way to preserve vision and reduce complications, including blindness.

Getting a routine comprehensive eye exam is the best way to diagnose glaucoma early. 

Summary

Open-angle glaucoma is the most common type of glaucoma. A clog in the drainage angle causes it, which disrupts the flow of eye fluid and results in an increase in eye pressure and optic nerve damage.

Open-angle glaucoma is a slow-progressing disease that doesn’t produce symptoms until advanced stages. This makes catching it early difficult. Warning signs of glaucoma include blurry vision and blind spots in peripheral (side) vision.

While it can’t be cured, open-angle glaucoma can be treated and managed with medication, laser therapy, and glaucoma surgery.