DescriptionAn in-depth report on the causes, diagnosis, treatment, and prevention of glaucoma.
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 chronic glaucoma. It may be particularly beneficial for patients with pseudoexfoliation glaucoma.
The standard procedures are usually one of the following:
African Americans may respond better to initial laser surgery better than to conventional trabeculectomy while the opposite may be true in Caucasians. Some experts now recommend that, in most circumstances, African Americans should start with laser surgery and Caucasians who have no serious medical problems should have trabeculectomy first.
In addition, a number of experimental and less invasive procedures are under development.
Filtration Surgery (Trabeculectomy)
The Procedure. Filtration surgery has been used for more than 100 years with only minor modifications. It employs conventional surgical techniques known as full-thickness filtering surgery or guarded filtering surgery (trabeculectomy).
Trabeculectomy involves the following:
The procedure has a high success rate; about 50% of patients no longer need medication, and 35% to 40% still need medication but have better control.
Side Effects. Many of the serious side effects or complications that occur with filtration surgery involve blebs.
Supportive Medication for Preventing Scarring. Specific agents, usually mitomycin C, are often used in conjunction with the procedure to prevent scarring and closure. A large meta-analysis on 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.Mitomycin also carries a risk for adverse effects and more research is required to determine long-term extent. The following are some that have been reported:
Other anti-scarring drugs being investigated include a monoclonal antibody, CAT-152, a genetically designed agent that acts like an immune factor to block transforming growth factor-beta (TGF-beta), which causes scarring. An early trial in 2002 was promising.
The Procedure. Laser trabeculoplasty involves the following steps:
In a two-year study, laser surgery of the trabecular meshwork reduced pressure by one third in 70% to 97% of patients. Patients will still need to take anti-glaucoma eyedrop medications every day.
Laser surgery is not a cure. Within two to five 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 rarely 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.
Implants 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. Success rates are highest (75% pressure control over 5 to 7 years) in appropriate patients. Drainage implants may be useful in the following conditions:
The Procedure. In general the procedure is as follows:
Complications. Complications include the following:
The implant often becomes blocked and repeated operations are needed. Some investigators are studying the use of an agent called tissue plasminogen activator (tPA) to open up tubes that have been blocked by blood or blood factors. (This so-called clot-busting drug is normally used to break up blood clots during heart attacks.) In one 2002 study, tPA prevented such blocks in 89% of eyes. Unfortunately, significant complications rates were high (11%).
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 deep sclerectomy, the surgeon removes a deep piece of the sclera (the white part of the eye), part of the trabecular meshwork, and the front of Schlemm's canal (the vessels that return fluid into the blood stream).
In general, they work as follows:
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. In time, however, these nonpenetrating techniques are expected to be as effective as filtration surgery.
Treatment for Patients with both Glaucoma and Cataracts
Cataracts and Glaucoma. For patients with both glaucoma and cataracts, experts recommend the following:
A major 2002 analysis suggested that the combined approach generally offers better control over eye pressure for patients with both cataracts and glaucoma. The best surgical procedures, however, is still uncertain. [For descriptions of Cataract surgery, see Well-Connected #26 report Cataracts.]
Laser Cyclophotocoagulation (or 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). These is a chance of vision loss with this procedure, so it is reserved for people with end-stage glaucoma or those who fail to benefit from any other therapies. Nevertheless, researchers continue to explore the possibilities for this effective procedure, especially for people who may not have access to expensive medications. Studies in 2002 suggest it may even be suitable as first-line surgery for some glaucoma patients.
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 eyedrops. It has almost completely replaced conventional surgery, which requires anesthesia and hospitalization.
Vision will be blurred and recovery can take four to eight weeks. Once surgery has been performed, such patients can usually use previously restricted anticholinergic medications, such as antihistamines and certain antidepressants, with safety.
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 descriptions of phacoemulsification and intraocular lens implantation, see Well-Connected #26 report Cataracts.]