Updated on  September 6, 2022
8 min read

What Causes Glaucoma

19 sources cited
Vision Center is funded by our readers. We may earn commissions if you purchase something via one of our links.

What is Glaucoma?

Glaucoma is an umbrella term that refers to a series of eye conditions that cause permanent damage to the optic nerve, which is the communication pathway between your eye and brain. 

Glaucoma is caused by fluid build-up in the front of the eye, leading to increased eye pressure on the optic nerve. This high pressure is also called ocular hypertension. If left untreated, it will cause irreversible damage and eventually blindness. 

Glaucoma, also called the "sneak thief of sight," is particularly dangerous. It often doesn't have any symptoms or warning signs until the advanced stage of the disease. For this reason, it is crucial to get routine eye exams from an optometrist or ophthalmologist. 

If found early, treatment can prevent vision changes and blindness. There currently is not a cure for glaucoma. If you are diagnosed with the condition, you will likely need to follow a treatment plan for the rest of your life. 

Who is at Risk of Developing Glaucoma?

Glaucoma affects over 3 million Americans and is the second leading cause of blindness worldwide. While people of any age can get glaucoma, those over 60 are at a much higher risk. People can have glaucoma in one or both eyes.

Family history and environmental risk factors play a significant role in people who develop glaucoma. 

These risk factors include:

  • Another family member with glaucoma
  • African American, Asian, and Hispanic populations
  • History of steroid use
  • Eye injury
  • Severe myopia (nearsightedness)
  • Hypertension (high blood pressure)
  • Thinner cornea (less than .5 mm)

Glaucoma Causes (By Type)

The front of your eyes produces a constant flow of clear liquid (aqueous humor) to help keep them nourished and healthy. This liquid is also responsible for eye shape and keeping the intraocular pressure (IOP) at a normal level. 

The liquid must drain out of the eye at the same rate it comes in to maintain a constant pressure. It does this through the drainage angle. If the balance is off even slightly, IOP can increase, causing glaucoma and permanent damage to the optic nerve.  

The most common types of glaucoma stem from problems with the drainage angle. Open-angle glaucoma and acute angle-closure glaucoma result in either a slowing of the drainage rate or a blockage of the drain. Both types cause high intraocular pressure

Other types of glaucoma can result from a different health condition or injury that causes the IOP to increase.

Open-Angle Glaucoma

Open-angle glaucoma is the most common type of glaucoma. It accounts for about 90% of all glaucoma cases.9 

Open-angle means that access to the drainage angle is open. The drainage angle is where the iris (controls how much light comes in) of the eye meets the cornea (clear covering on the front of the eye that allows light to go in).

Open-angle glaucoma is often associated with a gradual progression of increased IOP caused by a slowing drainage rate, similar to a clogged drain. 

Since it happens over time, there is typically no pain or symptoms to warn you of the increased IOP and damage to the optic nerve. The absence of symptoms can lead to a late diagnosis when vision loss has already started. 

Acute Angle-Closure Glaucoma

Angle-closure glaucoma is a less common type of glaucoma. It is caused by the iris slipping into a position that blocks the drainage angle. This blockage results in your eye pressure increasing rapidly, causing an acute attack.  

Angle-closure glaucoma is a medical eye emergency that needs to be treated by an ophthalmologist immediately before permanent vision loss or blindness occurs. 

Chronic angle-closure glaucoma can occur when the blockage slowly progresses over time, leading to a rise in eye pressure. The increase in eye pressure is often not detected until an acute attack sends a person to the doctor. If left untreated, it can cause blindness. 

Normal-Tension Glaucoma

Normal-tension glaucoma, also called low-tension glaucoma and normal-pressure glaucoma, is damage to the optic nerve not caused by increased eye pressure. 

People diagnosed with this type of glaucoma have normal eye pressure. It is currently considered a form of open-angle glaucoma. 

Many eye experts don't fully understand what causes normal-tension glaucoma, but poor blood circulation to the eye is a likely cause. 

People who have frequent migraines, low blood pressure, and people of Japanese descent also have an increased risk of developing normal-tension glaucoma. 

Pigmentary Glaucoma

Pigmentary glaucoma, which develops from pigment dispersion syndrome, happens when pigment material breaks free and clogs your drainage angle. Pigment material is what gives your eye color and is located on your iris. When the drainage angle is blocked, it can increase eye pressure, causing glaucoma.  

Pigmentary glaucoma is rare and often exacerbated by vigorous physical activity such as jogging or basketball in people with pigment dispersion syndrome. 

Being in your 20s and 30s puts you at an increased risk for developing pigmentary glaucoma. Being male and caucasian also puts you at a higher risk. 

Secondary Glaucoma

Secondary glaucoma occurs due to a secondary medical issue that causes the increase in eye pressure, such as: 

  • Eye injury
  • Inflammation
  • Diabetes
  • Certain medications 

Treatment for this type of glaucoma will include first treating the root cause of the IOP increase.

Common types of secondary glaucoma include:

  • Steroid-induced glaucoma. Usually from the use of steroid eye drops.
  • Trauma-induced glaucoma. Typically, blunt force trauma.
  • Uveitic glaucoma. Inflammation in the middle layer of the eye.
  • Neovascular glaucoma. Newly formed blood vessels cover the drainage angle. Typically, associated with diabetes. 

Congenital Glaucoma

Congenital glaucoma, also called childhood glaucoma, occurs when a baby’s drainage canal does not develop properly in-vitro. It is typically diagnosed within the first year of life and is often hereditary. It is a rare condition.

Symptoms of congenital glaucoma typically include:

  • Enlarged eyes
  • Cloudiness
  • Excessive tearing
  • Sensitivity to light

Surgery and medication are the gold standards to treat this type of glaucoma. Many babies with childhood glaucoma go on to live full lives. 

What are the Symptoms of Glaucoma? 

Often, especially with open-angle glaucoma, increased eye pressure doesn’t have any symptoms or warning signs until the optic nerve becomes damaged and the disease progresses. 

The first warning signs of open-angle glaucoma and normal-tension glaucoma are typically blind spots in your peripheral vision (side vision).

Angle-closure glaucoma is more acute because the IOP rises at a faster rate. 

Warning signs are usually noticeable right away and include:

  • Hazy or blurred vision
  • Severe pain in the eye or forehead
  • Eye redness
  • Rainbows or halos 
  • Headache
  • Nausea
  • Vomiting

If you have any of these symptoms, seek medical treatment right away. A delay in treatment could result in blindness.

Preventing Glaucoma

Glaucoma is a severe disease, but with routine eye exams, it can be prevented. 

Knowing your risk factors and the signs and systems can help stop the progress of glaucoma before vision loss occurs. Medicare covers a yearly glaucoma test for people in high-risk groups.

Since an eye injury can cause secondary glaucoma, it is essential to wear eye protection when working in a hazardous environment. 

Practicing good oral hygiene can also protect your eyes because glaucoma is linked to gum disease.

Additional critical steps you can take to prevent glaucoma include:

  • Get a routine comprehensive eye exam with dilation from a licensed ophthalmologist
  • Ask your family members if they have a history of glaucoma
  • Maintain a healthy weight and diet
  • Control your blood pressure
  • Stay physically active
  • Avoid smoking 
  • Keep tight control of your blood sugar if you have diabetes

Treatment Options for Glaucoma

Early detection is the key to stopping glaucoma. Diagnosis is made during a comprehensive eye exam by a licensed eye doctor. 

The eye exam will include a series of tests to look at: 

  • Intraocular pressure
  • The shape of the optic nerve
  • Wide field of vision
  • Drainage angle
  • Corneal thickness

Damage caused by glaucoma is permanent. However, there are treatment options available to help preserve eyesight and further the progression of the disease.


If you are diagnosed with glaucoma, you will likely use eye drop medicine daily. Medication helps decrease eye pressure by reducing the amount of fluid produced or helping stabilize the drainage rate. 

Other medications for glaucoma treatment include: 

  • Beta-blockers
  • Alpha agonists
  • Carbonic anhydrase inhibitors
  • Miotics

Glaucoma medication can cause side effects. If you use daily eye drops for glaucoma, be mindful of these potential side effects:

  • Itching or stinging
  • Red eyes
  • Heart rate fluctuation 
  • Breathing changes (especially in those with asthma )
  • Eyelash growth
  • Blurred vision
  • Changes in eye color
  • Loss of energy

Always give your doctor a list of medications you are taking, as some may interact with each other in negative ways. 

It is essential to take your glaucoma medicine every day, typically for the rest of your life, to prevent vision loss. 

Outpatient Laser Surgery 

Laser surgery is a standard treatment option for people diagnosed with glaucoma and, administered in an outpatient setting. 

There are two types of laser eye surgery used to treat glaucoma:

  • Trabeculoplasty. Repairs the drainage angle for better fluid flow.
  • Iridotomy. A small hole is created in the iris to help with fluid drainage.

Other Surgeries

Some glaucoma cases might need a more complex surgery administered in a formal operating room. This type of surgery is usually necessary to create a new drainage system.

Common glaucoma surgeries conducted in an operating room include:

  • Trabeculectomy. Creates a new drainage channel. 
  • Glaucoma drainage device. Implantation of a tiny drainage tube.
  • Cataract surgery. Removal of the natural lens to reduce eye pressure.
Updated on  September 6, 2022
19 sources cited
Updated on  September 6, 2022
  1. Definition of optic nerve.” National Cancer Institute. 
  2. What is Ocular Hypertension?” American Academy of Ophthalmology.
  3. Common Eye Disorders and Diseases.” Centers for Disease Control and Prevention.
  4. Don’t Let Glaucoma Steal Your Sight!” Centers for Disease Control and Prevention.
  5. Are You at Risk for Glaucoma?” Glaucoma Research Foundation.
  6. Aqueous Humor.” American Academy of Ophthalmology.
  7. Drainage Angle.” American Academy of Ophthalmology.
  8. What is Glaucoma? Symptoms, Causes, Diagnosis, Treatment.” American Academy of Ophthalmology. 
  9. Types of Glaucoma.” Glaucoma Research Foundation.
  10. Definition of iris.” National Cancer Institute.
  11. Definition of cornea.” National Cancer Institute.
  12. Normal-Tension Glaucoma.” Glaucoma Research Foundation. 
  13. What is Pigment Dispersion Syndrome?” American Academy of Ophthalmology.
  14. Pigment Dispersion Syndrome and Pigmentary Glaucoma.” Glaucoma Research       Foundation. 
  15. What is Secondary Glaucoma?” Glaucoma Research Foundation. 
  16. Secondary Glaucoma.” BrightFocus Foundation 
  17. Childhood Glaucoma.” Glaucoma Research Foundation. 
  18. 10 Things To Do Today To Prevent Vision Loss From Glaucoma.” American   Academy of Ophthalmology.
  19. Glaucoma Eye Drops.” American Academy of Ophthalmology.
Vision Center Logo
The information provided on VisionCenter.org should not be used in place of actual information provided by a doctor or a specialist.
linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram