What is glaucoma?

What is the purpose of glaucoma surgery?

Glaucoma is a chronic disease which causes gradual loss of vision as it worsens over time. Although we cannot cure glaucoma, we can treat it. The goal of all glaucoma treatment is to slow down progression and preserve vision. At this point in time, the only way we definitively know how to do this is by lowering the eye pressure. Therefore, the purpose of all treatment in glaucoma (medical, laser and surgical) is to lower the eye pressure.

In all types of glaucoma, elevated eye pressure is the most important risk factor for glaucoma progression and further loss of vision. Even in cases of so-called "normal tension glaucoma" in which the pressure is usually in higher part of the normal range, it is still advantageous to lower the eye pressure as much as possible (without making it too low) to preserve vision.

If you have glaucoma, you may need several types of glaucoma treatments and surgeries over the years to keep the glaucoma controlled.

How does glaucoma surgery lower the eye pressure?

Eye pressure is the result of the balance between production of aqueous fluid in the eye, and its drainage. Pressure builds up when the balance is disrupted, either by over-production of fluid or by obstructed drainage. Most types of glaucoma have some obstruction to outflow. The goal of surgery is to either improve the existing outflow pathway and make it work more efficiently, or bypass the existing pathway altogether.


Surgeries that improve the existing pathway, tend to be shorter with less complications. However, the resultant pressure lowering may not last as long or be as effective as with other types of surgeries. These types of surgeries are easily combined with cataract surgery and can be an excellent first step to lowering eye pressure. Some examples of this type of surgery, known as "angle surgery" or "MIGS" ("Minimally Invasive Glaucoma Surgeries") include:


Surgeries that bypass the existing pathways are of two different categories. One group features some new devices which shunt fluid from the inside of the eye to the potential space just under the surface tissue of the eye, creating a new drainage pathway. This is done with the help of tiny implanted tubular devices. The site where the fluid is shunted to is called a "bleb". It is seen as a slight elevation of the surface tissue of the eye (conjunctiva) and is usually hidden under the eyelid. These devices have been developed recently. Generally, they have more predictable results with lower complication rates compared to the traditional trabeculectomy surgery. They usually require less post-operative follow-ups and patients have faster visual recovery. However, the pressure-lowering effect may not be as long-lasting or as potent as with traditional surgeries. Some examples of this type of surgery, also known as "MIBS" ("Minimally Invasive Bleb-forming Surgeries") are:

Traditional Glaucoma surgeries

These surgeries make up the second broad group of surgeries that decrease eye pressure by creating an alternate drainage pathway:

  • Trabeculectomy is still considered the "gold-standard" of glaucoma surgery to which all other surgical methods are compared. When successful, it can lower pressure most effectively and sustainably compared to all the other modalities. However, it may not work well in certain patient groups (eg. younger patients), or certain types of glaucoma (eg. neovascular glaucoma). It generally has a higher complication rate than other surgeries. It can involve frequent post-operative visits and treatments to ensure a successful outcome.
  • The Ahmed®, Baerveldt® and ClearPath® are Glaucoma Drainage Devices (GDD) used for refractory or advanced glaucoma treatment. They consist of a large silicone plate with an attached tube. These devices are implanted inside the eye to provide an alternate drainage pathway that rarely gets obstructed by excessive scarring (the way trabeculectomy does). They work very well in cases where other surgeries have failed. They do not require as frequent follow-up, but visual recovery takes as long as it does with trabeculectomy. They complication rate is comparable to trabeculectomy.

Why are there so many different options for glaucoma surgery? How does my surgeon choose the right procedure for me?

In considering your best option for glaucoma surgery, there are many factors to consider. Some of these factors include:

  • Is this an acute or chronic type of glaucoma? What is the level of urgency?
  • Is the patient able to tolerate medications? either drops or pills? If a patient cannot tolerate most glaucoma drops, it might be best to opt for the procedure that is most likely to work without drops (eg. Trabeculectomy)
  • How old is the patient? Certain procedures can cause more bleeding in very elderly patients. (eg. Trabeculectomy, Ahmed implants)
  • Has the patient had any other types of glaucoma surgeries already? (eg. if a Trabeculectomy has failed, a PreserFlo™ Microshunt or an Ahmed implant would be a good next step).
  • Is there also a cataract to remove? It may be useful to do cataract surgery at the same time.
  • Does the patient have to travel a great distance for follow-up appointments? Procedures requiring less frequent follow-up and less post-operative care may be preferable. (eg. KDB Goniotomy, PreserFlo™ Microshunt)
  • How much risk is reasonable for this patient? If the glaucoma is very advanced, longer surgeries requiring more dissection may be higher risk for permanent vision loss. (eg. KDB goniotomy or XEN® implant surgery are shorter procedures that can be very effective in some types of glaucoma).

These are some of the considerations your surgeon will discuss with you to ensure that we choose the best option for you.

What surgical procedures are available at GEM Clinic?

Why aren't some glaucoma procedures available at GEM Clinic?

There are some glaucoma procedures that are not offered at GEM Clinic (eg. canaloplasty). This is because equipment for certain procedures or funding for newer devices is not yet available. Surgeons working in Manitoba have to be selective in order to get access to newer treatment modalities. Although we would like to have access to all that is available in the treatment of glaucoma, the WRHA will not fund every request and those requests which are made must come with a lot of evidence as to why this is medically necessary and whether there will be a cost savings. New devices are often very expensive and do not have a lot of studies behind them (by nature of being recently developed). Therefore, it has been challenging to gain access to newer technologies in glaucoma surgery.

However, the landscape in Manitoba has been improving over the last few years thanks to the efforts of EPSOM and our allies at Misericordia Health Centre. EPSOM (Eye Physicians and Surgeons of Manitoba - www.manitobaeyephysicians.ca) is our advocacy group and has successfully advocated for several new glaucoma surgical options in the last few years. We are hoping for ongoing government support to keep expanding our armamentarium in the fight against vision loss from glaucoma!

B221-2025 Corydon Avenue, Winnipeg, Manitoba, Canada, R3P 0N5

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