Surgery:

If medications do not control eye pressure, or if they create intolerable side effects, surgery may be necessary in a small percentage of people with glaucoma. The standard procedures are usually one of the following:

• Filtration surgery (trabeculectomy). This procedure opens the full thickness of the drainage area.
• Laser trabeculoplasty. This procedure partially opens the drainage area. It does not reduce pressure to the extent of trabeculectomy but it has fewer adverse effects.

Filtration Surgery (Trabeculectomy)

The Procedure. Filtration surgery has been used for more than 100 years with only minor modifications. It uses conventional surgical techniques known as full-thickness filtering surgery or guarded filtering surgery (trabeculectomy).

• The surgeon creates a sclerostomy, a passage in the sclera (the white part of the eye) for draining excess eye fluid.
• A flap is created that allows fluid to escape without deflating the eyeball.
• The surgeon may also remove a tiny piece of the iris (called an iridectomy) so that fluid can flow backward into the eye.
• A small bubble called a bleb nearly always forms over the opening, which is a sign that fluid is draining out. Although surgeons aim for a thick bleb, which poses less risk than a thin one for later leakage, paradoxically the ideal operation would have no bleb at all.

The procedure has a high success rate. About 50% of patients no longer need medication after surgery. Thirty-five to 40% of those who still need medication have better control of their glaucoma.

A newer instrument called a trabectome has allowed for a less invasive type of trabulectomy surgery. The trabectome procedure appears to be a safe and simple way to lower eye pressure. It can be performed before a traditional trabulectomy, if needed.

Side Effects. Many of the serious side effects or complications that occur with filtration surgery involve blebs (blister-like bumps).

• Bleb Leaks and Infections. Blebs, particularly thin ones, commonly leak. Leakage can occur early on or sometimes as late as months or years after surgery. Untreated, such leaks can be serious and even cause blindness. Late-onset leakage significantly increases the risk for infection as well as a number of other serious conditions, including bleeding, a flattening of the eye ball, and harmful inflammation. Surgical repair is the most effective way of managing leaking blebs, although drug therapies, pressure patching, and other nonsurgical techniques may be tried first. Due to the dangers of leaking blebs, doctors recommend lifelong monitoring after surgery. Unfortunately, the incidence of late-onset leaking blebs is increasing due to the use of drugs used in filtration surgery to prevent scarring, another complication.
• Scarring. In up to 20% of cases, scars form around the incision, closing up the drainage channels and causing pressure to rebuild. Scarring is a particular problem in young patients, African-Americans, and patients who have taken multiple drugs, have had an inflammatory disease, or have had cataract surgery. Releasing the surgical stitches used in the procedure may help prevent scarring and pressure build-up. A second procedure called bleb needling sometimes can open up the scarred area and restore drainage. With this technique, the tip of a very fine hypodermic needle is used carefully to cut loose the particles closing off the drainage area.
• Cataracts. The procedure is highly associated with the development of cataracts over time. Because cataracts are associated with glaucoma anyway, it is not entirely clear whether the cataracts are caused by the surgery or would develop in any case.

Supportive Medication for Preventing Scarring. Specific drugs, usually mitomycin C, are often used in conjunction with the procedure to prevent scarring and closure. A large review of studies of mitomycin C supported its effectiveness in increasing surgical success in nearly all patients. Fluorouracil (5-FU) appears to be similar in effectiveness but has a high risk for complications and is not used as often as in the past.

Laser Trabeculoplasty

The Procedure. Laser trabeculoplasty involves the following steps:

• The procedure uses an instrument, usually a YAG laser, to burn 80 - 100 tiny holes in the drainage area.
• A tiny scar forms, which increases fluid outflow.
• The procedure takes 15 minutes, causes almost no discomfort, and has very few complications.

Laser surgery is not a cure. Patients still need to take anti-glaucoma eye drop medications every day. Within 2 - 5 years, about half of patients need either additional surgery or new medications.

Complications. In about 35% of patients, pressure increases after surgery. In most cases it is temporary, but in rare cases the increased pressure is permanent and vision loss can occur. Use of the drug apraclonidine (Iopidine) or pilocarpine can help prevent this elevated pressure. About a third of patients also develop adhesive-like substances called peripheral anterior synechiae that cause the iris to stick to part of the cornea.

Drainage Implants (Tube Shunts)

Drainage implants, also known as tube shunts, may be used to drain fluid in certain cases, such as if glaucoma is not responsive to any standard procedure or is caused by certain conditions.

Candidates. Drainage implants may be useful in the following conditions:

• Glaucoma caused by swelling in the iris
• Glaucoma caused by abnormal vessel formations
• Iridocorneal endothelial (ICE) syndrome

The Procedure. In general, the procedure involves:

• An implant, most commonly a 1/2 inch silicone tube, is inserted into the eye's front chamber (anterior).
• The tube drains the fluid onto a tiny plate that is sewn to the side of the eye.
• Fluid collects on the plate and then is absorbed by the tissues in the eye.

Complications. Complications include:

• Hypotony (very low eye pressure) is a serious complication that has been reduced using better techniques and improved implants.
• Cataracts, detached retina, breakdown of the cornea, and bleeding are potentially significant complications.
• There is also a risk for eye movement disorders, such as strabismus (crossed eyes) or diplopia (double-vision).

The implant often becomes blocked, and additional surgery may be needed.

Nonpenetrating Surgical Techniques: Deep Sclerectomy and Viscocanalostomy

Deep sclerectomy and viscocanalostomy are less invasive techniques than filtering surgery that leave the anterior chamber (front of the eye) intact and avoid creation of blebs.

In both deep sclerectomy and viscocanalostomy, the surgeon creates a flap in the outer part of the sclera (the white part of the eye) and then removes a deep piece of the sclera underneath.

Many variations are under investigation. In general, the procedures have fewer complications afterward than standard filtering surgery, although they require excellent surgical skill. Nonpenetrating techniques do not lower IOPs as much as conventional surgery does, however.

Treatment for Patients with both Glaucoma and Cataracts

Cataracts and Glaucoma. For patients with both glaucoma and cataracts, doctors recommend:

• In patients with cataracts and poorly controlled glaucoma, a two-step procedure for both eye conditions is needed. Typically the patient will first have a trabeculectomy for glaucoma, followed by cataract surgery such as phacoemulsification (lens removal through ultrasound). Fluid leakage and the presence of blood in the back chamber of the eye are potential complications of this combined procedure.
• Phacoemulsification is sometimes combined with viscocanalostomy in a procedure called phacoviscocanalostomy.
• In patients who have cataracts plus either closed-angle glaucoma or open-angle glaucoma that is stabilized with medication, the cataract may be able to be extracted and medication continued for the glaucoma.

Some evidence indicates that the combined approach generally offers better control over eye pressure for patients with both cataracts and glaucoma. However, it is still unclear which specific type of surgical procedure works best. [For more information, see In-Depth Report #26: Cataracts.]

Laser Cyclophotocoagulation (Cycloablation) for End-Stage Glaucoma

Diode laser transscleral cyclophotocoagulation (TSCPC), also called laser cycloablation, reduces aqueous production by destroying the muscles that control the lens for near and far vision (the ciliary body). There is a chance of vision loss with this procedure, so it is generally reserved for people with end-stage glaucoma or those who fail to benefit from any other therapies.

Surgery for Acute Closed-Angle Glaucoma

For an acute closed-angle glaucoma attack, emergency microsurgery is usually necessary after reducing pressure with medications.

Iridotomy or Iridectomy. Either laser (iridotomy) or conventional (iridectomy) surgery may be used. With either procedure an ophthalmologist makes a tiny opening in the iris to let the aqueous humor flow out more freely. Because acute glaucoma commonly occurs later in the other eye, surgeons will often recommend surgery in the unaffected eye to prevent a second attack.

Laser iridotomy almost never requires hospitalization, and postsurgical treatment includes only aspirin and eye drops. It has almost completely replaced conventional surgery, which requires anesthesia and hospitalization.

Vision will be blurred, and recovery can take 4 - 8 weeks. Following surgery, patients can usually safely use previously restricted anticholinergic medications, such as antihistamines and certain antidepressants.

Phacoemulsification and Intraocular Lens Implantation. Phacoemulsification and intraocular lens implantation, a procedure ordinarily used for cataracts, may prove to be beneficial for some patients with acute angle-closure glaucoma requiring surgery. [For more information, see In-Depth Report #26: Cataracts.]