Glaucoma is the leading cause of irreversible blindness in Canada — yet nearly 40% of those affected don't know they have it. This comprehensive guide covers what glaucoma is, who is at risk, how it is diagnosed, and the most effective treatments available today.
Glaucoma is not a single disease but a group of eye conditions that progressively damage the optic nerve — the vital cable that transmits visual information from your eye to your brain. This damage is most commonly caused by elevated intraocular pressure (IOP), though it can occur even when eye pressure is within the normal range.[1]
What makes glaucoma particularly dangerous is its insidious nature. In the most common form — open-angle glaucoma — there are no pain signals and no early visual disturbances. By the time a person notices vision changes, significant and irreversible optic nerve damage has already occurred. This is why glaucoma has earned the sobering nickname: the silent thief of sight.
In Canada, glaucoma is the leading cause of irreversible vision loss.[2]A landmark 2024 study using data from the 2016–2019 Canadian Health Measures Survey found that approximately 2.5% of Canadians aged 40–79 self-reported a glaucoma diagnosis, while 16.3% were classified as "glaucoma suspects" based on objective measurements. Critically, nearly 40% of those with definite glaucoma were entirely unaware of their condition.[3]
Why Regular Eye Exams Are Critical
Because glaucoma causes no pain and no early symptoms, the only way to detect it early is through comprehensive eye exams that include IOP measurement, optic nerve assessment, and visual field testing. The Canadian Association of Optometrists recommends annual eye exams for adults over 65 and every 1–2 years for adults aged 20–64.
Globally, approximately 80 million people have glaucoma as of 2020, with open-angle glaucoma affecting around 60 million of them.[4]Projections suggest this number will rise to 193 million by 2060 as populations age worldwide.[5]Glaucoma accounts for 8.39% of all cases of blindness globally — making it the second leading cause of blindness after cataracts, and the leading cause of irreversible blindness.[6]
Understanding which type of glaucoma is present is essential for selecting the right treatment. Each type has a distinct mechanism, progression pattern, and set of warning signs.
The most common form. Fluid drains too slowly, causing IOP to rise gradually over years. Often called the 'silent thief of sight' because there are no early symptoms.
The iris blocks the drainage angle. The acute form is a medical emergency with severe eye pain, headache, nausea, and halos around lights.
Optic nerve damage occurs despite normal IOP. More common in people of Japanese descent. May be related to reduced blood flow to the optic nerve.
Pigment granules shed from the iris clog the drainage angle. Exercise can trigger IOP spikes. More common in young, myopic men.
Acute angle-closure glaucoma deserves special mention because it is a medical emergency. If you or someone you know experiences sudden severe eye pain, headache, nausea, blurred vision, or halos around lights, seek emergency eye care immediately. Untreated acute angle-closure can cause permanent vision loss within hours.[7]
While glaucoma can affect anyone, certain factors significantly increase the likelihood of developing the condition. Identifying your personal risk profile is the first step toward proactive eye health management.[8]
* Relative risk contribution — not absolute probability. Multiple risk factors compound.
Having one or more of these risk factors does not mean you will develop glaucoma, but it does mean you should discuss more frequent eye exams with your optometrist. In Ontario, OHIP covers annual comprehensive eye exams for adults over 65 and for patients with diagnosed ocular conditions — making regular monitoring accessible for those at highest risk.
The symptom profile of glaucoma varies dramatically by type. Open-angle glaucoma — the most common form — produces no noticeable symptoms until significant vision loss has already occurred. This is the central challenge in glaucoma management: by the time most patients notice something is wrong, up to 40% of optic nerve fibers may already be irreversibly damaged.[9]
No symptoms whatsoever
Subtle peripheral blind spots (often unnoticed)
Tunnel vision — central vision preserved until late
Severe vision loss or blindness
Sudden, severe eye pain
Intense headache (often one-sided)
Nausea and vomiting
Blurred or hazy vision
Halos or rainbow rings around lights
Eye redness
⚠️ Go to emergency immediately if you experience these symptoms
The peripheral vision loss in open-angle glaucoma is particularly deceptive because the brain compensates by filling in the missing areas. Many patients only notice the loss when it becomes severe enough to affect daily activities like driving or reading. This is why regular comprehensive eye exams — not just vision screenings — are the only reliable way to detect glaucoma before permanent damage occurs.
Diagnosing glaucoma requires a comprehensive eye examination that goes well beyond a simple vision check. Your optometrist or ophthalmologist will typically perform several tests to assess different aspects of eye health.[10]
Measures intraocular pressure (IOP). Normal range is 10–21 mmHg. Elevated pressure is a key risk factor but not diagnostic on its own.
Direct examination of the optic nerve head. The doctor looks for a large cup-to-disc ratio (≥0.7) or asymmetry between eyes — signs of nerve damage.
Automated perimetry maps peripheral vision to detect blind spots (scotomas). Essential for monitoring progression over time.
Optical coherence tomography provides high-resolution cross-sectional images of the retinal nerve fiber layer (RNFL), detecting thinning before vision loss occurs.
Measures central corneal thickness. Thin corneas (<555 μm) are associated with higher glaucoma risk and can cause IOP to be underestimated.
Examines the drainage angle between the iris and cornea using a special lens. Determines whether the angle is open or closed — critical for classifying glaucoma type.
A comprehensive glaucoma assessment typically takes 45–90 minutes and may include dilating eye drops that temporarily blur your near vision for 2–4 hours. Bring sunglasses and arrange for someone to drive you home if possible. In Ontario, these exams are covered by OHIP for patients over 65 or those with a diagnosed eye condition. For others, the cost is typically $80–$150 at an optometry clinic.
There is currently no cure for glaucoma, and vision lost to optic nerve damage cannot be restored. However, treatment can effectively slow or halt progression in most patients. The goal of all glaucoma treatment is to lower intraocular pressure to a "target IOP" — a level at which the optic nerve is unlikely to sustain further damage.[11]
Medicated eye drops are the most common first-line treatment for open-angle glaucoma. They work by either reducing the production of aqueous humor (the fluid inside the eye) or improving its drainage. Most patients require one or more drops daily for life.[12]
| Drug Class | Examples | IOP Reduction | Frequency | Key Side Effects |
|---|---|---|---|---|
| Prostaglandin AnaloguesFirst Choice | Latanoprost, Bimatoprost, Travoprost | 25–33% | Once daily (evening) | Eye colour change, longer lashes, eye redness |
| Beta-Blockers | Timolol, Betaxolol | 20–27% | Once or twice daily | Slowed heart rate, breathing difficulties |
| Alpha-2 Agonists | Brimonidine | 18–25% | Twice or three times daily | Dry mouth, fatigue, eye allergy |
| Carbonic Anhydrase Inhibitors | Dorzolamide, Brinzolamide | 15–22% | Twice or three times daily | Metallic taste, tingling in fingers |
| Rho Kinase Inhibitors | Netarsudil (Rhopressa) | 20–25% | Once daily | Eye redness, corneal deposits |
Selective Laser Trabeculoplasty (SLT) has emerged as a viable first-line treatment, with some guidelines now recommending it before or alongside eye drops. The procedure uses short pulses of low-energy laser light to improve drainage through the trabecular meshwork. It is performed in-office, takes about 5–10 minutes per eye, and has minimal recovery time.[13]
When eye drops and laser treatment are insufficient to control IOP, surgical options are considered. Traditional glaucoma surgery (trabeculectomy) creates a new drainage pathway and can achieve the largest IOP reductions, but carries higher risks including infection, cataract formation, and hypotony (IOP that is too low). Minimally Invasive Glaucoma Surgery (MIGS) procedures offer a safer profile with more modest IOP reduction and are increasingly used in Canada, often combined with cataract surgery.[14]
The following chart compares the approximate IOP-lowering efficacy of common glaucoma treatments. The "target IOP" for each patient is individualized based on the stage of glaucoma, baseline IOP, and rate of progression. Most patients require a 20–30% reduction from baseline.
Source: Canadian Health Measures Survey 2016–2019 (Jin et al., 2024)[3]
A glaucoma diagnosis is life-changing, but it does not mean inevitable blindness. With consistent treatment and monitoring, the vast majority of patients retain functional vision for their lifetime. The key is adherence — studies show that poor adherence to eye drop regimens is one of the most common reasons for disease progression.
Set a daily alarm. Use the same time each day. If you miss a dose, take it as soon as you remember — but never double up. Nasolacrimal occlusion (pressing the inner corner of your eye for 1–2 minutes after instilling drops) reduces systemic absorption and side effects.
Glaucoma requires lifelong monitoring. Your doctor will check IOP, repeat visual field tests, and review OCT scans at regular intervals — typically every 3–12 months depending on stability. Never skip these appointments even if you feel fine.
Regular aerobic exercise can modestly lower IOP. Avoid activities that significantly raise IOP such as heavy weightlifting or inverted yoga poses. Sleeping with your head slightly elevated may also help. Avoid tight neckwear that can compress jugular veins.
Wear protective eyewear during sports and high-risk activities. Avoid eye injuries, which can cause secondary glaucoma. Inform all healthcare providers about your glaucoma, as some medications (including steroids) can raise IOP.
Support resources in Canada include the Fighting Blindness Canada helpline and patient registry, as well as the Canadian Glaucoma Society, which provides patient education materials and connects patients with specialists. Many hospitals in the GTA also offer low vision rehabilitation services for patients with significant vision loss.
In Ontario, glaucoma care is typically a team effort. Your optometrist is usually the first point of contact for detection and monitoring, while ophthalmologists (medical eye doctors) perform laser procedures and surgery. For complex or advanced cases, glaucoma subspecialists at academic medical centres such as the Krembil Eye Institute at Toronto Western Hospital provide specialized care.
The clinics below offer advanced diagnostic technology — including OCT imaging and visual field testing — that is essential for glaucoma monitoring. Use the Eye Clinic Directory to search by specialty, location, and available technology.
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