As with drops and lasers, the purpose of glaucoma surgery is to reduce IOP. While there are many types of glaucoma surgery, they all do one of two things:

1. Decrease the amount of fluid produced by the eye
2. Increase the amount of fluid draining out of the eye

Decrease the amount of fluid produced by the eye:

Endocyclophotocogulation (ECP) is similar to cyclophotocoagulation. The main difference is that that ECP is performed with the laser placed into the eye and applied directly onto the ciliary body, which is the structure that produces fluid. Because the laser applied much closer to the target, less overall laser energy is needed compared to cyclophotocoagulation. Therefore, On the other hand, because ECP is a surgical procedure, it has the same risks as other surgeries.

Increase the amount of fluid draining out of the eye:

Trabeculectomy

In this surgery, the surgeon creates a small flap in the second layer of the wall of the eye (sclera) to allow fluid to leave the eye in a controlled manner. The flap is then covered with the outer layer of the eye (conjunctiva). Nothing is implanted into or onto the eye. During and/or after the surgery, the surgeon may use medications to keep the flap from scarring down. After surgery, a fluid pocket called a bleb forms between the conjunctiva and sclera. Your surgeon pays close attention to the appearance of the bleb as well as to your IOP in order to decide how well the surgery is working. Typically, the bleb stays hidden under the upper eyelid.

Glaucoma drainage devices

A glaucoma drainage device has a tube and a plate. The tube is inserted into the eye via a tiny pathway, and the plate is sutured onto the wall of the eye. The tube is then covered with donated tissue. Fluid then drains out of the eye onto the plate, which also forms a bleb. The tube and plate are generally hidden under the upper or lower eyelid.

The two commonest glaucoma drainage devices in use are:

1. Ahmed Glaucoma Valve®
2. Baerveldt Glaucoma Implant®

The decision about which valve to use is based on several factors that your surgeon will discuss with you.

Minimally Invasive Glaucoma Surgery (MIGS)

MIGS are a new and growing area of glaucoma surgery. In general, most MIGS involve placing a tiny device into or onto the eye in order to drain fluid. There are a number of such devices including XEN45®, iStent®, Trabectome®, InnFocus Microshunt®, Ex-PRESS Mini Glaucoma Shunt®, and Kahook Dual Blade® to name a few. The main advantage of these devices is that the surgeries tend to be less invasive than trabeculectomies and glaucoma drainage devices. We are still learning more about the role of MIGS in glaucoma treatment long term.

Risks of Glaucoma surgeries

The main risks of all glaucoma surgeries are:

1. Infection inside the eye
2. Bleeding inside the eye
3. IOP too high or too low
4. Inflammation inside the eye

Additional risk associated with trabeculectomy are:

1. The bleb can cause discomfort and/or dry eyes
2. The bleb may leak, thus requiring surgery to repair it
3. The bleb may be too elevated or too flat

Additional risks associated with glaucoma drainage devices are:

1. Double vision
2. Discomfort
3. Blurry vision due to swelling of the clear window of the eye (cornea)
4. The tube can erode through the conjunctiva

Due to these risks, patients need to be seen very regularly during the first days and weeks after surgery to detect, prevent, and treat these potential complications. Moreover, the actual surgery is only the first step towards getting control of your IOP. The remainder of the fine tuning is done during the aftercare visits to your doctor’s office. Your doctor may adjust your medications and/or do other small procedures at each visit.