Updated on  September 8, 2023
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What Causes Glaucoma

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Glaucoma affects about 3 million Americans and is the second leading cause of blindness worldwide.4 There are many types of glaucoma, all of which involve optic nerve damage.

The optic nerve is the communication pathway between the eye and the brain. Damage to this nerve can result in vision loss and blindness.

The most common type of glaucoma, open-angle glaucoma, usually doesn't cause early symptoms. For this reason, about 50% of people with glaucoma don't know they have it.4

Main Cause of Glaucoma

Glaucoma develops when the optic nerve is damaged. This nerve damage is usually caused by increased pressure inside the eye, called intraocular pressure. However, some people get glaucoma with normal eye pressure.

main cause of glaucoma

Increased eye pressure happens when there's a buildup of aqueous humor — the fluid that flows throughout the front part of your eye. Normally, aqueous humor flows through the pupil to the front of your eye, then drains through channels between your iris and cornea. This area is called the drainage angle. 

Elevated eye pressure occurs when the drainage system doesn't work properly or the eye produces too much fluid.

Open-angle glaucoma and closed-angle 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. 

Types of Glaucoma

Glaucoma symptoms, causes, and treatments vary depending on the type of disease you have.

Open-Angle Glaucoma

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

In open-angle glaucoma, the drainage angle between the iris and cornea remains open. However, other parts of the drainage system don't function properly. This causes pressure in the eye to increase gradually.

Since it happens over time, there are typically no symptoms to warn you of open-angle glaucoma. The absence of symptoms can lead to a late diagnosis when vision loss has already started. 

Angle-Closure Glaucoma (Narrow-Angle Glaucoma, Closed-Angle Glaucoma)

Also called narrow-angle glaucoma or closed-angle glaucoma, angle-closure glaucoma is caused by the iris slipping into a position that blocks the drainage angle. This blockage causes pressure in the eye to increase. 

Angle-closure glaucoma can occur gradually or suddenly. 

When the drainage angle gets completely blocked, eye pressure can increase rapidly. This leads to an acute glaucoma attack.

Acute Angle-Closure Glaucoma

Although it's rare, an acute angle-closure attack is a medical emergency that can lead to blindness. 

Call your eye doctor immediately if you experience signs of acute angle-closure glaucoma:

  • Sudden blurry vision
  • Severe eye pain
  • Headache
  • Nausea and vomiting
  • Rainbow colored rings or halos around lights 

Normal-Tension Glaucoma

When you have normal-tension glaucoma, damage to the optic nerve is not caused by increased eye pressure. 

People diagnosed with this type of glaucoma have normal eye pressure. Many eye experts don't fully understand what causes optic nerve damage in these cases. Poor blood circulation to the eye is a likely cause.

Secondary Glaucoma

Secondary glaucoma occurs due to a medical issue that causes an increase in eye pressure. Conditions that can lead to secondary glaucoma include:

  • Eye injury
  • Inflammation
  • Diabetes
  • Cataracts
  • Certain medications

Pigmentary Glaucoma

Pigmentary glaucoma falls under the umbrella of secondary glaucomas. It happens when pigment material breaks off from the iris and clogs your drainage angle. When the drainage angle is blocked, eye pressure increases and causes damage to the optic nerve.

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

Congenital Glaucoma

Congenital glaucoma, also called childhood glaucoma, falls under the umbrella of secondary glaucomas. It occurs when a baby’s drainage canal doesn’t develop properly. This rare condition is typically diagnosed within the first year of life and is often hereditary.

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

Who is at Risk of Developing Glaucoma?

Certain medical conditions and lifestyle factors can contribute to elevated eye pressure, increasing the risk of developing glaucoma. These risk factors include:

Family History of Glaucoma

If your parents, grandparents, siblings, or other close relatives have glaucoma, you are much more likely to develop the condition. According to the Glaucoma Research Foundation, family history increases the risk of glaucoma four to nine times.5

African American, Asian, and Hispanic Populations

Certain ethnic backgrounds are at higher risk than Caucasians to develop glaucoma. For instance, one survey found that in the United States, glaucoma is six times more prevalent in individuals of African descent than in the European American (EA) population in some age groups.20

History of Steroid Use

Steroid-induced iatrogenic glaucoma was described for the first time in the 1950s. This research shows that long-term corticosteroid use can cause an elevation in eye pressure.21

Eye Injury

Trauma to the eye is also a risk factor for glaucoma. This is also called traumatic glaucoma. A significant blow to the eye—such as in a car accident— can cause an elevation in eye pressure, which may lead to glaucoma if left untreated.

Other Risk Factors

Other risk factors of glaucoma include the following:

  • Being over age 55
  • Severe myopia (nearsightedness)
  • Hypertension (high blood pressure)
  • Thinner cornea (less than .5 mm)

What are the Symptoms of Glaucoma? 

Most people with glaucoma don't have symptoms until they start to lose their eyesight. Symptoms vary based on the type and stage of the disease.

Open-Angle Glaucoma Symptoms

This type doesn’t cause symptoms in the early stages. The first warning signs of open-angle glaucoma are typically blind spots in the peripheral vision (side vision).

Advanced glaucoma will cause blind spots in the central vision as well.

Angle-Closure Glaucoma Symptoms

Acute angle-closure glaucoma causes noticeable symptoms right away because eye pressure rises at a faster rate.

Symptoms include:

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

If you have any of these symptoms, call your eye doctor right away. Acute angle-closure glaucoma is a medical emergency that can result in permanent vision loss.

Normal-Tension Glaucoma Symptoms

Similar to open-angle glaucoma, this type doesn’t cause early symptoms. Later symptoms include blurred vision and a loss of peripheral vision.

Pigmentary Glaucoma Symptoms 

Symptoms of this type include:

  • Blurred vision that gets worse with exercise 
  • Halos around lights 
  • Gradual loss of peripheral vision 

Congenital Glaucoma Symptoms

Symptoms of congenital glaucoma typically include:

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

Secondary Glaucoma Symptoms

Symptoms of secondary glaucoma vary depending on the underlying problem causing it. Depending on the cause, you may experience symptoms similar to open-angle glaucoma or angle closure glaucoma.

Glaucoma Diagnosis

Early detection is the key to stopping glaucoma, which is why routine eye exams are critical. Your eye doctor can diagnose glaucoma during a comprehensive eye exam.

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

Preventing Glaucoma

Glaucoma is a severe disease, but with routine eye exams, it can be prevented. Some ways to prevent the progression of glaucoma include:

Regular Eye Exams

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

Eye Protection

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

Lifestyle Changes

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

You can’t cure glaucoma. However, early detection is the key to stopping the disease. A licensed eye doctor can diagnose glaucoma during a comprehensive eye exam. 

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
  • Visual acuity test

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


If you are diagnosed with glaucoma, you will likely use prescription eye drops daily. Medication helps decrease eye pressure by reducing fluid production or helping stabilize the drainage rate.

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

Medications for glaucoma treatment include:

  • Beta-blockers
  • Alpha agonists
  • Carbonic anhydrase inhibitors
  • Miotics
  • Prostaglandins
  • Rho-kinase inhibitors

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 daily, 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. It is administered in an outpatient setting.

There are two types of laser treatment 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.

Other surgeries that treat glaucoma 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.


Open-angle glaucoma has no cure. Glaucoma treatment can help manage the condition and preserve your eyesight. The outlook for secondary glaucoma depends on the underlying cause of the condition. 

Closed-angle glaucoma is a medical emergency that requires immediate treatment to save your vision. Babies with congenital glaucoma typically live normal lives when surgery is performed early.


Glaucoma is a serious eye condition that can lead to permanent vision loss if not treated in time. Fortunately, routine comprehensive eye exams and preventive steps can help prevent glaucoma before it takes hold.

If you have been diagnosed with glaucoma, treatment options are available. Consult your eye doctor to know which option is best for you.

Updated on  September 8, 2023
21 sources cited
Updated on  September 8, 2023
  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.
  20. Siegfried CJ, Shui YB. "Racial Disparities in Glaucoma: From Epidemiology to Pathophysiology." Mo Med, 2022.
  21. Feroze KB, Zeppieri M, Khazaeni L. "Steroid Induced Glaucoma." StatPearls Publishing, 2023.
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