Surgery involves either laser treatment or making a cut in the eye to reduce the intraocular pressure (IOP). The type of surgery your doctor recommends will depend on the type and severity of your glaucoma and the general health of your eye. Surgery can help lower pressure when medication is not sufficient, however it cannot reverse vision loss.
Doctors often recommend laser surgery before filtering microsurgery, unless the eye pressure is very high or the optic nerve is badly damaged. During laser surgery, a tiny but powerful beam of light is used to make several small scars in the eye’s trabecular meshwork (the eye’s drainage system). The scars help increase the flow of fluid out of the eye.
In contrast, filtering microsurgery involves creating a drainage hole with the use of a small surgical tool. When laser surgery does not successfully lower eye pressure, or the pressure begins to rise again, the doctor may recommend filtering microsurgery.

Filtering Microsurgery

When medicines and laser surgeries do not lower eye pressure adequately, doctors may recommend a procedure called filtering microsurgery (sometimes called conventional or cutting surgery).
In filtering microsurgery, a tiny drainage hole is made in the sclera (the white part of the eye) in a procedure called a trabeculectomy or a sclerostomy. The new drainage hole allows fluid to flow out of the eye and helps lower eye pressure. This prevents or reduces damage to the optic nerve.
Pain during the microsurgery

In most cases, there is no pain involved. The surgery is usually done with a local anesthetic and relaxing medications. Often a limited type of anesthesia, called intravenous (I.V.) sedation, is used.
In addition, an injection is given around or behind the eye to prevent eye movement. This injection is not painful when I.V. sedation is used first. The patient will be relaxed and drowsy and will not experience any pain during surgery.
Success rate

Most of the related studies document follow-up for a one year period. In those reports, it shows that in older patients, glaucoma filtering surgery is successful in about 70-90% of cases, for at least one year.
Occasionally, the surgically-created drainage hole begins to close and the pressure rises again. This happens because the body tries to heal the new opening in the eye, as if the opening were an injury. This rapid healing occurs most often in younger people, because they have a stronger healing system. Anti-wound healing drugs, such as mitomycin-C and 5-FU, help slow down the healing of the opening. If needed, glaucoma filtering surgery can be done a number of times in the same eye.
Outpatient procedure

Usually, filtering surgery is an outpatient procedure, requiring no overnight hospital stay. Within a few days after surgery, the eye doctor will need to check on the eye pressure. The doctor will also look for any signs of infection or increase in inflammation.
Recovery Time

For at least one week after surgery, patients are advised to keep water out of the eye. Most daily activities can be done, however, it is important to avoid driving, reading, bending, and doing any heavy lifting.
Each case is different, so check with your doctor for specific advice.
Appearance of the eye after surgery

The eye will be red and irritated shortly after surgery, and there may be increased eye tearing or watering. The inner eye fluid flows through the surgically-created hole and forms a small blister-like bump called a bleb. The bleb, usually located on the upper surface of the eye, is covered by the eyelid, and is usually not visible.
Changes in vision and medication

There may be some vision changes, such as blurred vision, for about six weeks after the surgery. After that time, vision will usually return to the same level it was before surgery.
Vision can sometimes improve after surgery in patients who had been using pilocarpine. After stopping pilocarpine drops, the pupil returns to normal size, allowing more light to enter the eye.
In a few cases, the vision may be worse due to very low pressure. Cataracts or wrinkle in the macula area of the eye may develop.
After surgery, you may need to change your contact lenses or glasses. Gas permeable or soft contact lenses may be worn. However, the bleb may cause fitting problems, and special care will be needed to avoid infection of the bleb. Contact lens users should discuss these problems with their eye doctor following surgery.

Laser Surgery

Laser surgeries have become important in the treatment of different eye problems and diseases.
During the laser surgery, the eye is numbed so that there is little or no pain. The eye doctor then holds a special lens to the eye. The laser beam is aimed into the eye, and there is a bright light, like a camera flash.
Risks of Laser Surgery

Laser surgery is still surgery, and can carry some risks. Some people experience a short-term increase in their intraocular pressure (IOP) soon after surgery. In others who require YAG CP (Cyclophoto-Coagulation) surgery, there is a risk of the IOP dropping too low to maintain the eye’s normal metabolism and shape. The use of anti-glaucoma medication before and after surgery can help to reduce this risk.
The following are the most common laser surgeries to treat glaucoma.
Laser Peripheral Iridotomy (LPI)

For the treatment of narrow angles and narrow-angle glaucoma.
Narrow-angle glaucoma occurs when the angle between the iris and the cornea in the eye is too small. This causes the iris to block fluid drainage, increasing inner eye pressure. LPI makes a small hole in the iris, allowing it to fall back from the fluid channel and helping the fluid drain.
Argon Laser Trabeculoplasty (ALT):

For the treatment of primary open angle glaucoma (POAG).
The laser beam opens the fluid channels of the eye, helping the drainage system work better. In many cases, medication will still be needed.
Usually, half the fluid channels are treated first. If necessary, the other fluid channels can be treated in a separate session another time. This method prevents over-correction and lowers the risk of increased pressure following surgery.
Argon laser trabeculoplasty has successfully lowered eye pressure in up to 75% of patients treated.
Selective Laser Trabeculoplasty (SLT)

For the treatment of primary open angle glaucoma (POAG).
SLT uses a combination of frequencies that allow the laser to work at very low levels. It treats specific cells “selectively,” leaving untreated portions of the trabecular meshwork intact. For this reason, it is believed that SLT, unlike other types of laser surgery, may be safely repeated many times.
Neodymium: YAG laser cyclophotocoagulation (YAG CP)

An alternative to filtering microsurgery that is typically used later in the treatment algorithm. This surgery destroys part of the ciliary body, the part of the eye that produces intraocular fluid. The procedure may need to be repeated in order to permanently control glaucoma.
Pain or discomfort from glaucoma laser surgery

There is a slight stinging sensation associated with LPI and ALT. In YAG CP laser surgery, a local anesthetic is used to numb the eye. Once the eye has been numbed, there should be little or no pain and discomfort.
Long-term benefits of glaucoma laser surgery

Glaucoma laser surgeries help to lower the intraocular pressure (IOP) in the eye. The length of time the IOP remains lower depends on the type of laser surgery, the type of glaucoma, age, race, and many other factors. Some people may need the surgery repeated to better control the pressure IOP.
Medication following laser surgery

In most cases, medications are still necessary to control and maintain eye pressure. However, surgery may lessen the amount of medication needed.
Recovery time

In general, patients can resume normal daily activities the next day after laser surgery.
The procedure is usually performed in an eye doctor’s office or eye clinic. Before the surgery, your eye will be numbed with medicine. Your eye may be a bit irritated and your vision slightly blurry after the surgery. You should arrange a ride home after your surgery.
Increased risk of cataracts

There is a small risk of developing cataracts after some types of laser surgery for glaucoma. However, the potential benefits of the surgery usually outweigh any risks.
There is a common myth that lasers can be used to remove cataracts; this is not the case except in experimental studies. After a cataract has been taken out with conventional cutting surgery, there often remains an outer membrane lens capsule. This membrane can slowly thicken and cloud vision, just as the cataract did. Laser surgery can open this membrane, helping to clear vision without an operation. This laser procedure is called a capsulotomy.
It is important to discuss all of your questions or concerns about laser surgery with your eye doctor.