Glaucoma is a disease of the eye that damages the retina and optic nerve from increased pressure within the eyeball. Since glaucoma can cause blindness, you need to detect and treat it immediately. Find out how.

What is glaucoma?

Glaucoma occurs when the retina is damaged from increased pressure inside the eye. The retina is essential for vision because it captures the images we see and transmits them to the optic nerve, which then delivers the images to the brain. When pressure inside the eye increases, damage to the retina and optic nerve leads to a gradual loss of peripheral vision. In some cases, glaucoma can also cause blindness.

Glaucoma causes and types

The eye contains a fluid called aqueous humour that provides it with the nutrients it needs . This liquid is produced and circulates inside the eye before draining through a small canal that empties into the bloodstream. If too much aqueous humour is produced or if the liquid doesn’t drain properly, pressure in the eye increases, which leads to a condition called ocular hypertension. This hypertension, which is different from arterial hypertension, can affect just one or both eyes. 

There are different types of glaucoma, depending on how the fluid is kept from draining.

Open-angle glaucoma

In 90% of cases, fluid obstruction in the eye is gradual and goes unnoticed. However, this type of glaucoma causes permanent damage in the long term. 

Narrow-angle glaucoma

In 10% of cases, fluid is completely and suddenly obstructed, and intraocular pressure increases sharply. This type of glaucoma is very painful and is a medical emergency. You must go to the hospital right away as only surgery can prevent vision loss. Other symptoms of narrow-angle glaucoma are sudden blurred vision, eye redness and pain, dilation of one or both pupils, sensitivity to light, sudden headache, and nausea or vomiting.

Who can develop glaucoma?

Glaucoma affects 1% of people over the age of 40. The disease also increases with age, affecting 4% of people aged 80 or over. Black people also develop glaucoma more often. We don’t know exactly why certain people get glaucoma, but the disease has a major genetic component. Diabetes, hypertension, hypothyroidism and nearsightedness are risk factors. Glaucoma may also occur after trauma (e.g., a blow to the head), be caused by a tumour near the eye, or be caused by certain medications (e.g., prolonged corticosteroid use).

Glaucoma symptoms and detection

Open-angle glaucoma starts slowly and gradually. It has no symptoms. If the disease has advanced before you get a diagnosis, you may notice a slight decrease in your field of vision. Screening by an eye care professional (optometrist or ophthalmologist) is the only way to confirm glaucoma and avoid its complications. 

Since vision loss from glaucoma is permanent and irreversible—and since glaucoma is the second leading cause of blindness in the world—, you need to get regular eye checkups even if you don’t have vision problems. Vision loss can have a significant impact on your daily activities (i.e., your ability to drive a car).  

Your eye care professional will measure the pressure in your eye with a device called a tonometer. Your specialist will also test your visual field and check the back of your eye to see if the optic nerve has been damaged. 

There is no way to prevent glaucoma. Frequent screening is the only way to detect the disease before it damages the eye. Screening tests must be done every year for people over the age of 40, particularly people with a parent who had or has glaucoma.

Glaucoma treatment

There are three types of glaucoma treatment: medication, traditional surgery and laser surgery. Your ophthalmologist will determine the best treatment for your situation.


Medication can't cure glaucoma or repair existing damage, but it can stop the disease from progressing. Medication controls eye pressure to prevent or stop vision loss by reducing the amount of aqueous humour produced or by helping this fluid to drain. 

Some medications come in the form of tablets, but these are generally not prescribed anymore. Doctors tend to prescribe topically applied treatments with eye drops.

Tips for applying eye drops

Glaucoma can be controlled through the daily and consistent use of eye drops. To prevent damage, you must use these medications every day for life while following the recommendations of your eye care professional.

  • Put the drops in your eyes using the techniques that your pharmacist showed you.
  • If you have to apply multiple drops, wait at least 5 minutes between applications (one drop at a time) to let the medication fully absorb into the eye.
  • Use your index finger to put pressure on the inner corner of your eye for about 1 minute. This will help the medication penetrate into the eye and prevent it from entering the bloodstream, which can cause side effects in the rest of the body. Try to keep your eyelid shut for about 5 minutes.
  • Don’t touch your eye with the tip of the eye drop bottle to avoid contaminating it. Once opened, the bottle has a very specific expiration date, as it doesn’t contain preservatives (which would cause too many side effects for the eye). Your pharmacist can confirm the bottle’s exact expiration date, but in general, these medications can be used for up to 30 days after opening. Don’t go by the manufacturer’s expiration date on the bottle.

Did you know?
Your optometrist can renew or adjust your glaucoma prescription in collaboration with your ophthalmologist.

Side effects of eye drops

Like any medication, eye drops can cause side effects. In this case, the side effects include tingling, burning or itching of the eye, glare, or blurred vision. These symptoms usually occur when the drops are applied. They generally don’t last very long (less than 5 minutes) and tend to decrease after you’ve used the product for a few weeks.

Some medications, even when applied directly to the eye, can be absorbed into the blood and cause side effects in the rest of the body. If you have new symptoms and you don’t know what’s causing them, talk to your pharmacist.

Caution: Be careful with over-the-counter (OTC) medications 

Some medications, such as cold and flu or allergy medicine, can block the flow of aqueous humour and aggravate glaucoma. See your pharmacist before buying OTC medications.

In all Quebec pharmacies, OTC medications carry a drug caution code  that indicates the precautions to take when using them. People who suffer from glaucoma should avoid caution code “B.” Ask your pharmacist for more information about drug caution codes.


The goal of traditional surgery or laser surgery is to make an opening in a specific location of the eye so that the aqueous humour can drain. Surgery is generally indicated for people who don’t respond well to medication or who have narrow-angle glaucoma.

If you have glaucoma, remember that your pharmacist is a great partner to help you manage your medication and maintain your eye health.

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