What is Glaucoma?

Glaucoma is a group of eye diseases which lead to progressive degeneration of the optic nerve and can cause gradual irreversible vision loss if not detected and treated early.1

Glaucoma is the second leading cause of blindness globally, behind cataracts, with primary open-angle glaucoma accounting for about half of cases. Glaucoma decreases quality of life, impacting patients physically, emotionally, and socially.

Primary open-angle glaucoma occurs in about 45 million individuals and is responsible for about 8.4 million cases of blindness worldwide.2

What is Glaucoma?

Development of Glaucoma

Normal Eye
Normal Eyeball

Flow of aqueous humour through the drainage canal

Glaucoma Eyeball

Drainage canal blocked:
build up of fluid

Damaged Eye
Damaged Eyeball

Increased pressure damages blood vessels and optic nerve

Causes of Glaucoma

Glaucoma is caused by damage to the optic nerve, which is a bundle of nerve fibers located at the back of the eye that carries visual information from the eye to the brain. As the nerve fibers in the optic nerve gradually deteriorate, you will experience blind spots in your vision.

Optic nerve damage in glaucoma is usually the result of increased pressure in the eye, which is caused by a buildup of fluid (also called aqueous humour) in the eye. In a healthy eye, this fluid normally circulates within the eye and drains out through a tissue called the trabecular meshwork, located at the angle between the iris and the cornea.

Overproduction or improper drainage of the aqueous humour increases in the eye pressure because the fluid is not flowing out at its normal rate, and this increase in pressure damages the optic nerve.4

Types of Glaucoma

There are several types of glaucoma, including1,3:


Primary open-angle glaucoma


Angle-closure glaucoma


Pigmentary glaucoma


Secondary glaucoma


Normal-tension glaucoma

1. Primary Open-Angle Glaucoma

Primary open-angle glaucoma (POAG) is the most common form of glaucoma. The eye is constantly circulating and draining fluid, called aqueous humor. When there is a build-up of aqueous humor in the eye due to over-production or improper drainage, it puts pressure on the optic nerve which can lead to a loss of vision over time.

2. Angle-Closure Glaucoma

Angle-closure glaucoma, also known as closed-angle or narrow angle glaucoma, is less common. It occurs when the drainage angle in the eye closes or becomes blocked, preventing aqueous humor from draining. Angle-closure glaucoma can occur gradually or suddenly and is typically considered a medical emergency because it can cause vision loss within one day.

3. Pigmentary Glaucoma

Pigmentary glaucoma occurs when pigment granules from the iris build up in the eye’s drainage channels and block or reduce fluid drainage. Activities such as jogging can sometimes cause the pigment granules to move around to cause this blockage, resulting in intermittent eye pressure elevations.

4. Secondary Glaucoma

Secondary glaucoma can develop in response to external factors, such as injury, infection, tumor, or medication, causing the intraocular pressure to rise.

5. Normal-Tension Glaucoma

In normal-tension glaucoma, the optic nerve is damaged, but the intraocular pressure stays within the normal range. Not much is known about why this type of glaucoma occurs.

Glaucoma in Children

Children and infants may have glaucoma, which can either be present from birth or develop in the first few years of life. Much like other types of glaucoma, the optic nerve damage may be caused by reduced/blocked drainage or an underlying medical condition.

Child having eyes examined

Glaucoma Symptoms

Glaucoma symptoms vary depending on the primary cause of the disease. Glaucoma is called the “silent thief of sight”, since any changes in vision usually go undetected until the disease is in an advanced stage.3


Open-angle types of glaucoma have no early warning signs or symptoms until the disease has progressed to the point of peripheral (side) blind spots or vision loss. Regular eye exams can help with earlier detection because eye doctors will routinely check eye pressure and retinal or optic nerve damage. As the disease advances, symptoms may include:

  • Blind spots in your peripheral (side) or central vision in both eyes
  • Tunnel vision

Doctor conducting an eye test with the patient


Angle-closure glaucoma typically occurs as a sudden attack, rather than a gradual onset. If you are experiencing the following symptoms, you should see your eye doctor as soon as possible:

  • Severe eye or forehead pain
  • Eye redness
  • Decreased or blurred vision
  • Seeing rainbows or halos (rings) around lights
  • Headache
  • Nausea and vomiting
Doctor examining patients eyes

Risk Factors

Glaucoma occurs very gradually and is often in advanced stages before any symptoms begin to appear. It’s important to be aware of risk factors so that your eye doctor can routinely examine you for early indications of glaucoma. Risk factors include1,3:

Age: the risk is increased in those over the age of 40

High Intraocular Pressure
(High internal eye pressure)

Extreme farsightedness or nearsightedness

Long-term use of steroid medications, especially eyedrops

Thinning of the optic nerve

Race: glaucoma is more prevalent people with African, Hispanic or Asian heritage

Family history of glaucoma

Previous eye injury

Corneas that are thin in the center

Certain medical conditions including diabetes, migraines, high blood pressure or sickle cell anemia

happy mother and daughter


There are several steps you can take to detect glaucoma in its early stages, which is important in preventing or slowing the progress of vision loss.3

Regular comprehensive eye examinations: your eye doctor can perform routine tests to detect glaucoma as early as possible.

Know your family’s eye health history: glaucoma tends to run in families, so if you know you have an increased risk you may need more frequent screening.

Exercise safely: regular, moderate exercise may help prevent glaucoma by reducing eye pressure.

Wear eye protection: in some cases, glaucoma is caused by eye injury, so wear eye protection when using power tools or playing certain sports.

Take prescribed eyedrops regularly: eyedrops prescribed for high eye pressure can significantly reduce the risk of developing glaucoma, but in order to be effective these must be used as prescribed, even if you aren’t experiencing symptoms.

Treatments Available for Glaucoma

Glaucoma is treated by lowering eye pressure. There are several options available for glaucoma treatment. These include1:

1. Medications

Prescription eye drops are a common treatment for glaucoma. These are intended to increase fluid drainage in the eye, reducing intraocular pressure (IOP) and preventing optic nerve damage.

Oral medications may also be prescribed to reduce eye pressure, if eye drops alone are ineffective.

Patient receiving eye drops

2. Laser Therapy

Laser trabeculoplasty, which temporarily increases the eye’s efficiency in draining fluid, is an option for open-angle glaucoma. Your doctor will use a small laser beam to reopen the clogged trabecular meshwork (drainage channel).

Laser Therapy

3. Surgery

  • Trabeculectomy is the creation of a drainage flap in the eye that facilitates fluid drainage.
  • Tube shunts are small tubes inserted in the eye to drain away excess fluid, lowering eye pressure.
  • Micro-invasive glaucoma surgery (MIGS) is another surgical option to lower eye pressure, and is typically less invasive and requires less postoperative care than other glaucoma surgeries.

Talk to your eye doctor for more information about glaucoma treatment options.

Introducing PRESERFLO™ MicroShunt

PRESERFLO™ MicroShunt is a tiny, soft, flexible stent that helps your eye drain excess fluid, and may help lower eye pressure and prevent further vision loss.

Learn More


  1. Canadian Association of Optometrists (CAO). Glaucoma, the silent thief of sight. Available from https://opto.ca/health-library/about-glaucoma. Accessed on January 27, 2021.
  2. Data on file. Glaukos Inc. 2021.
  3. Mayo Clinic. Glaucoma symptoms & causes. Available from https://www.mayoclinic.org/diseases-conditions/glaucoma/symptoms-causes/syc-20372839. Accessed on March 5, 2021.
  4. American Academy of Ophthalmology (AAO). Causes of glaucoma. Available from https://www.aao.org/eye-health/diseases/glaucoma-causes. Accessed on March 5, 2021.