There are several types of glaucoma that present different symptoms. By far, the most common type of glaucoma is called primary open-angle glaucoma. It is known as the silent theft of sight because there are no symptoms in its early stages.

Last Updated: March 28, 2023

Video: Glaucoma

Glaucoma, The Silent Thief of Sight

Glaucoma is a group of diseases that affect the optic nerve in the eye which can result in irreversible vision loss.1 It is one of the leading causes of blindness, affecting more than 450,000 Canadians.2

There are several types of glaucoma that present different symptoms. By far, the most common type of glaucoma is called primary open-angle glaucoma. It is known as the silent theft of sight because there are no symptoms in its early stages.

What are the symptoms of glaucoma?3,4

People with early stage glaucoma are often not aware of it themselves until it progresses to the later stages. However, early stage glaucoma can be detected during a routine eye exam. Early detection and treatment is crucial in preventing progression towards vision loss. As the condition progresses, it leads to a loss of side vision or peripheral vision and eventually tunnel vision which may interfere with daily activities such as driving. If left untreated, permanent vision loss may occur.

Depending on the type of glaucoma, other symptoms include:

  • blurry vision
  • eye redness
  • eye pain
  • light sensitivity
  • halos around lights
  • tearing
  • nausea
  • vomiting
  • headache
  • rapid progression to vision loss

What are the different types of glaucoma?3-5

  • Primary open-angle glaucoma is the most common type of glaucoma accounting for approximately 90% of all cases. It generally develops painlessly and gradually without early warning signs. Primary open-angle glaucoma is associated with increased pressure in the eye. The increased pressure is thought to put mechanical stress on the back of the eye resulting in damage to the optic nerve.
  • Angle-closure glaucoma is an uncommon but serious condition that can occur chronically (progressing gradually) or acutely (appearing suddenly). Angle-closure glaucoma occurs when the drainage system inside the eye becomes blocked. This results in a buildup of fluid within the eye, an increase in eye pressure and damage to the optic nerve. Angle-closure glaucoma is often associated with symptoms such eye redness, pain, blurry vision, nausea, vomiting and headaches. It is a medical emergency as it can cause vision loss within a day.
  • Secondary glaucoma occurs as the result of an injury, surgery, infection or tumor in or around the eye that causes an increase in eye pressure. It may also be the result of certain medical conditions, medications and eye abnormalities.
  • Normal-tension glaucoma occurs when the eye pressure stays within the “normal” range, but the optic nerve is still damaged. The cause of this condition is still being explored and it is speculated to be due to poor vascular perfusion leading to damage to the optic nerve.

Who is at risk of developing glaucoma?6

Individuals with the following are at an increased risk for developing glaucoma:

  • Elevated eye pressure
  • Increased age
  • Family history of glaucoma
  • Physical injury or surgery to the eye
  • Cardiovascular conditions (such as high blood pressure, low blood pressure, heart conditions, etc.)
  • Certain eye-related conditions (such as decreased optic nerve tissue, retinal detachment, eye tumors, eye inflammation, etc.)

How is glaucoma detected?

Without telling symptoms, a routine eye exam is often the only way to detect glaucoma. During an eye exam, the pressure inside the eyes is measured. Using special equipment, the optometrist looks directly inside the eye to inspect for any damage to the optic nerve and retinal layers. Other imaging and testing may be conducted to measure any functional vision loss and structural changes in the eye.

How is glaucoma treated?3-5

A number of medications are available to treat glaucoma. Generally, it is in the form of eye drops intended to reduce the elevated eye pressure. A single medication may be prescribed or a combination of medications. The type of medication may change if it is not providing enough pressure reduction or due to its adverse effects.

A number of procedures are available to reduce eye pressure. Surgery may help lower eye pressure when treatment with medication is not enough. Some surgical options include laser trabeculoplasty, trabeculectomy, drainage implants and laser peripheral iridotomy.

  • Laser Trabeculoplasty helps to drain fluid out of the eye. A laser beam is used to open up the drainage system of the eye to reduce eye pressure and prevent optic nerve damage. The results may be temporary and the procedure may need to be repeated.
  • Trabeculectomy is a filtering surgery that involves creating a drainage flap. The flap allows fluid from the eye to drain into a small blister on the surface of the eye called the bleb, which empties out to the vascular system of the body. This reduces eye pressure to prevent further damage to the optic nerve.
  • Drainage implants is another surgical option where a small silicone tube is inserted in the eye to help drain the excess fluid buildup in the eye and to reduce eye pressure. It may be appropriate for people with uncontrolled glaucoma, secondary glaucoma and children with glaucoma.
  • Laser Peripheral Iridotomy is a procedure that creates a small hole in the iris to allow fluid drainage into the different compartments of the eye to reduce eye pressure. This procedure is done to prevent and treat angle-closure glaucoma.

Treatment with daily eye drops or surgery is usually effective at maintaining vision. However, once vision is lost due to glaucoma, it cannot be restored. Since the disease can progress or change silently, compliance with treatment and routine eye exams are essential. Routine eye exams with your optometrist are highly recommended to screen for glaucoma.

Video: What is glaucoma and eye pressure? | Dr. Jessica Ng


  1. Weinreb RN et al. The pathophysiology and treatment of glaucoma: a review. JAMA. 2014;311(18):1901-1911. doi: 10.1001/jama.2014.3192.
  2. Statistics Canada. (2010). Healthy Aging Indicators. Retrieved from Statistics Canada: Available from:
  3. Weinreb RN et al. Primary open-angle glaucoma. Lancet. 2004;363(9422):1711-1720.
  4. Jackson J et al. (2010). Care of the patient with primary angle closure glaucoma. Retrieved from American Optometric Association:
  5. Group, CNTGS. The effectiveness of intraocular pressure reduction in the treatment of normal-tension glaucoma. Am J Ophthalmol. 1998;126(4):498-505.
  6. Gordon MO et al. The Ocular Hypertension Treatment Study: baseline factors that predict the onset of primary open-angle glaucoma. Arch Ophthalmol. 2002;120(6):714-720.