When a patient with glaucoma who has a pressure that is too high and causing damage to their vision, despite receiving the maximum amount of medication that can be tolerated, the decision is made to have glaucoma surgery. Trabeculectomy is the most common form of glaucoma surgery used to treat open angle glaucoma. During trabeculectomy, an opening is created in the eye and partially covered with a flap of tissue. This new opening allows fluid to drain out of the eye bypassing the clogged drainage channels that are malfunctioning in patients with glaucoma. Studies have found that trabeculectomy significantly reduces vision loss and lowers eye pressure.

However, many people need another trabeculectomy or other glaucoma surgery because the surgery may fail either early or much later because the body closes the drain created by the surgeon. The surgery is also less likely to work in patients with darker pigmentation, children who have congenital glaucoma, people with difficult to control glaucoma with new blood vessels growing on the iris, diabetes or persons with prior eye surgery. As a result, the investigators need to find ways to improve the longterm survival of trabeculectomy surgery in all patients.

The usual treatment is to not have an injection of Bevacizumab on the third through fifth day after trabeculectomy surgery. Topical anaesthetic drops to numb the eye will be given, prior to being given the tested medicine. Once the eye has been anaesthetized, the medication will be injected into the potential space created during the glaucoma surgery, also called a bleb, using a standard small syringe. The patient will receive an injection of either 1.25mg (0.05ml) of Bevacizumab or Balanced Salt Solution (BSS) into the trabeculectomy bleb that had been created in the surgery. Participants will be randomly (by chance) placed in one of the 2 study groups. There will be a 50% chance of being placed in either group. There will be 60 people who will participate in this study at 2 centres throughout the Toronto region. The length of this study for participants is 12 months, and the entire study is expected to take about 18 months to complete.

Inclusion Criteria:

• Age more than 18 years old
• Patients with glaucoma that is inadequately controlled on maximal tolerated medical therapy and scheduled for trabeculectomy surgery (with/without combined cataract extraction)
• Decision makers fluent in English
• Decision makers able to understand and read consent form

Exclusion Criteria:

• Patients with active intraocular inflammation/uveitis or neovascular glaucoma
• History of previous trabeculectomy surgery or prior retinal detachment with scleral buckle placement in the surgical eye
• Aphakia in surgical eye
• Pregnant and nursing women
• Unable to fulfill inclusion criteria
• Refusal of consent