If medicine or laser surgery does not relieve eye pressure, a patient may need glaucoma surgery. There are several options.
Filtering surgery creates a new path through the eye's tissues to let fluid drain from the eye.
In the most common filtering surgery, called a trabeculectomy or a sclerostomy, the surgeon makes a small opening in the white part of the eye (the sclera) to create a new outflow path. The fluid then flows through the new opening and creates a bleb, which is like a small bubble or reservoir on the surface of the eye. The bleb holds the fluid while it is slowly absorbed into the surrounding tissue. The upper eyelid usually hides the bleb, so it's not noticeable to you or others.
Most people who have this procedure no longer need medicine after surgery. Some people treated still need medicine, but they have better pressure control after the surgery. About 15 percent do not benefit from filtering surgery.
An alternative type of glaucoma surgery may occasionally be performed in which the tissues over the drainage area are thinned but not fully penetrated. This procedure may produce fewer complicatons than trabeculectomy, but also may be less effective in achieving low intraocular pressures.
Drainage implant surgery is sometimes performed when a person is not suited for filtering surgery or when earlier filtering surgery has failed. Depending on the kind of implant used, the surgery is called valve, shunt or seton surgery.
In these procedures, the surgeon inserts a tiny tube through the sclera into the front part of the eye behind the iris. This tube becomes a path for fluid to drain away. The other end of the tube is attached to a tiny reservoir that acts like the bleb to hold fluid until it is absorbed into the surrounding tissue. The reservoir is placed on the surface of the eye, back between the eye muscles, so it is not visible.
Right after filtering or drainage implant surgery, a person may have a temporary decrease of vision. Vision usually improves over several weeks to its previous level. It also takes time to recuperate from either form of surgery. For example, in the weeks after surgery, people often must avoid getting water into their eyes, reading, bending, lifting heavy objects and driving.
Canaloplasty is a newer procedure to lower pressure that is performed within the eye wall but that does not actually pentrate the eye. While this procedure is safer that filtering surgery, it does not provide as profound a reduction in IOP.
Minimal Invasive Glaucoma Surgeries are a set of newer FDA approved procedures that lower pressure. These approaches currently include Trabectome and the iStent. Both of these approaches work by bypassing the blockage in the drain of the eye to help fluid flow through the natural drain and do not require "artifical" pathways for fluid drainage to areas outside the eye. Like canaloplasty, the procedures are less risky than filtering surgery but do not provide as profound a reduction in IOP. More long-term data is needed to determine how well they work beyond the first few years. Use of Minimal Invasive Glaucoma Surgeries is still being debated among glaucoma specialists but may have application is specific patients.
Laser Cyclophotocoagulation is used for severe cases of glaucoma. It eliminates tiny areas of the ciliary body that make aqueous fluid. This "turns down the faucet." Laser cyclophotocoagulation requires a numbing block to the eye to prevent pain with the procedure
Glaucoma surgeries have some possible risks, such as:
Unfortunately, the new drainage path can close, causing pressure in the eye to rise again. Filtering surgery can be repeated with good results. Also, drainage implants are often successful in patients whose filtering surgery has failed. The medicines that reduce inflammation and control scar formation after surgery have helped increase the success of glaucoma surgeries.