Glaucoma

Glaucoma is the second most common cause of vision loss in seniors in Canada. More than 250,000 Canadians have chronic open-angle glaucoma, the most common form of the disease. The good news is, however, that with early detection and treatment one can usually prevent significant vision loss.

Glaucoma occurs due to damage to the optic nerve. While it is not known exactly how this occurs, there is an association between damage to the optic nerve and pressure within the eye due to build up of excess fluid within the eye. Lowering pressure within the eye is in fact the main method of treating glaucoma.

High eye pressure is not always a sign that you have glaucoma but may be an indication you are at risk of developing it. On the other hand, it is possible to have glaucoma even if you have "normal" pressure within the eye. Measuring eye pressure alone is therefore not an indicator of whether one has glaucoma. A complete eye examination conducted by an eye doctor is necessary for a diagnosis of glaucoma.

Over time the disease develops into a loss of peripheral (side) vision. If glaucoma is untreated it could advance to later stages where central vision narrows to "tunnel" vision, or it may result in complete loss of vision. Early detection and treatment is essential to prevent severe vision loss or blindness.

Types of Glaucoma + Risk Factors

Primary Glaucoma

Open-angle glaucoma accounts for 90 per cent of all cases in Canada – Initially you can perform all normal daily activities such as driving and reading and vision loss is not obvious until it is too late and permanent. With primary open-angle glaucoma, the normal drainage outflow mechanism in the eye becomes blocked, increasing fluid pressure inside the eye. However, some people may have what is called normal tension glaucoma, a type of open angle glaucoma in which damage to the optic nerve may occur even though the pressure within the eye is not elevated.

Primary acute closed-angle glaucoma results from a buildup of fluid in the eye because the distance between the iris and the drainage system has been closed, stopping fluid from draining from the eye. This type of glaucoma occurs very suddenly and is an emergency. There is often severe pain associated with this condition. Severe vision loss can occur if treatment is not sought immediately.

Chronic angle closure glaucoma also involves a narrowing of space between the iris and the drainage system but it occurs much more gradually than in the acute form of the condition (and can take weeks or even years). There are no symptoms other than vision loss.

Secondary Glaucoma can result from a variety of other conditions such as an eye injury or inflammation, eye surgery complications, diabetes and the use of certain medications.

Symptoms:

Primary open-angle glaucoma and chronic angle closure glaucoma have no symptoms other than eventual vision loss. Vision will appear normal and there is no pain. A person may not be aware they have glaucoma for a long time, despite the fact that they are losing vision slowly.

Acute closed-angle glaucoma occurs with a sudden onset of symptoms such as severe eye pain, blurred vision, nausea, redness in the eye and haloes around lights.

Risk Factors:

Although researchers do not have a definitive picture of what causes glaucoma, they have identified a number of factors that may put a person at greater risk of developing glaucoma. These are:

  • Elevated pressure in the eye. People with higher than average pressure in the eye have an elevated risk of developing glaucoma.
  • Family history. People with a family history of glaucoma are at a much higher risk of developing open-angle glaucoma.
  • Age – after age 40 and after age 60. It is fairly common to develop glaucoma over the age of 40, with the risk increasing significantly for people over the age of 60
  • Ethnicity. People of African descent are at a higher risk of developing open-angle glaucoma. Angle closure glaucoma is more common in people of Asian and Inuit ethnicity.
  • Myopia. People who are nearsighted have an increased risk of developing glaucoma.

Because early treatment of glaucoma is essential in preventing vision loss, it is important to have regular eye exams to monitor for this condition. Speak to your eye doctor about how often you should get your eyes checked. People with any of the risk factors just described should have more frequent eye examinations.

Treatment:

Primary open-angle glaucoma can be treated. The goal of treatment is the lowering of pressure within the eye. This can be achieved through eye drops, laser treatment or surgery.

Eye Drops: Your doctor may prescribe one or more eye drops to lower pressure within the eye. It is important that you use the eye drops exactly as prescribed, even though the routine may be challenging, since some drops are used once a day and others more frequently. Research has shown that missing a day or two of eye drop use can lead to an increase in pressure within the eye, putting one at risk of losing vision.

Laser Treatment (Selective Laser Trabeculoplasty – SLT): A special type of laser is used to create very small holes within a region of the eye called the trabecular meshwork. This process increases drainage of the fluid within the eye and thereby lowers pressure within the eye. This treatment may work for a few years, but often has to be repeated to prolong the effect. Very often one still has to use eye drops to maintain the decrease in pressure but usually one can use fewer medications than before laser treatment. SLT is usually carried out in the ophthalmologist's office.

Surgery

  • Conventional surgery. This procedure involves creating a channel for fluid to flow out of they eye or inserting a tube to allow the fluid to drain. Surgery must be done in the hospital and each eye is treated at separate surgical visits. The surgical procedure is 60 – 80 per cent effective and a second operation may be needed if the drainage hole closes. Your ophthalmologist will explain the full range of possible side effects that this surgery may have. These may include slight vision loss, cataracts, corneal problems, shadows in vision, inflammation and infection within the eye.
  • Minimally Invasive Glaucoma Surgery (MIGS). This procedure is usually performed at the same time as cataract surgery although it can be conducted as a separate surgery. It involves the insertion of an extremely tiny tube within the eye (from the inside out) to facilitate drainage of fluid from the eye. It is usually recommended for people who suffer from mild to moderate glaucoma. It usually results in a decrease in the number and frequency of eye drops needed to control the pressure within the eye. This is particularly attractive to people who have difficulty managing a large number of medications. Studies have shown these devices to be effective for up to four years post surgery but since the procedure is relatively new it is not yet known what the long-term effectiveness will be. There are three different tubes from three different manufacturers being used for this procedure. CNIB makes no attestation to whether any of these devices works any better than any other device. Your ophthalmologist will be able to explain the differences between them to you. The three devices currently approved for sale in Canada are:
    • iStent inject®
    • XEN® Gel Stent
    • Cy-Pass® Micro-Stent

Helpful links:

The following websites contain useful information on glaucoma: