In open-angle glaucoma, aqueous humor, the fluid that normally flows in and out of the eye, has difficulty leaving through the eye's sponge-like drainage system, the trabecular meshwork. When this occurs, pressure within the eye, called intraocular pressure, builds up and may damage the optic nerve and lead to vision loss. Medications, laser surgery, or other glaucoma surgeries may be used to lower and control the eye pressure.
When is surgery necessary?
When medications or laser treatment cannot lower eye pressure caused by glaucoma, surgery is usually recommended. Of the possible procedures, glaucoma filtration surgery, also called trabeculectomy, is the most common.
How is Trabeculectomy done?
A small flap is made in the sclera (or white) of the eye. A filtration bleb, or reservoir, is created under the conjunctiva, the thin, clear coating covering the sclera. The aqueous humor inside the eye can drain through the flap and collect in the bleb, where it is then absorbed into the lymph and blood vessels around the eye.
After the bleb is carefully constructed, the incision is closed with tiny stitches. Some of these stitches may be removed or cut with a laser after surgery to increase fluid drainage.
Drugs to reduce scarring are often applied during and after surgery.
The bleb looks like a bump or blister on the with of the eye, but is usually hidden by the upper eyelid.
Fluid drains from the inside of the eye into the bleb.
What can you expect if you have surgery?
► Before Surgery
You will continue to use your glaucoma medications until just prior to surgery. If you take aspirin or any aspirin-containing products, these should be discontinued 10-14 days prior to your eye surgery.
► The Day of Surgery
A trabeculectomy is done in an outpatient operating room with a local anesthetic to prevent discomfort during the operation. You may also be given a sedative to relax you. General anesthesia is rarely necessary. The procedure is usually performed in less than an hour, but it may take longer if you have had a previous eye surgery, or if your eye is inflamed or abnormal blood vessels are present.
► After Surgery
Postoperative care is as important to the long-term success of the operation as the surgery itself. In follow-up appointments, your ophthalmologist (Eye M.D.) will examine the filtering bleb, the external appearance of the eye, your eye pressure, and the back of your eye. You should avoid lifting, bending, or straining after surgery, until your eye pressure stabilizes.
Pain is unusual after surgery, although your eye may feel tender and sensitive. A non-aspirin pain reliever is usually sufficient to treat any discomfort. Sudden, severe, or deep-seated pain, especially if it is associated with loss of vision, should be reported to your ophthalmologist immediately.
Eye pressure is adequately controlled in three out of four people. Although follow-up visits are still necessary, many people no longer need to use eye drops. However, if the opening closes or too much fluid drains from the eye, additional surgery may be necessary.
What will my vision be like?
Vision may fluctuate daily after surgery. Generally your vision is blurry for several weeks. There may or may not be a change in your glasses prescription after surgery.
If a cataract is present or another complication exists, vision may not return to what it was before surgery. Surgery cannot restore vision already lost from glaucoma.
As with all surgeries, there are risks associated with a trabeculectomy. One of the most common complications is scarring. Other complications include:
► loss of vision
Although the success rate is quite high, sometimes a single surgical procedure cannot halt the progression of glaucoma. Another surgery and/or continued treatment with medications may be necessary.
An eye that has undergone a trabeculectomy and has a functioning bleb will always be susceptible to infection. A red, uncomfortable eye may be a sign of infection and needs to be attended to urgently.
Are there alternatives to glaucoma filtration surgery?
When the risk is high that a trabeculectomy will fail, especially in neovascular glaucoma or glaucoma associated with inflammation in the eye, an aqueous shunt surgery may be recommended. An aqueous shunt is a small tube or valve placed in the eye through a tiny incision. This shunt drains excess fluid into a small reservoir placed on the eye.
This surgery, like a trabeculectomy, is an outpatient surgical procedure. Risks of surgery and postoperative care are similar to those for a trabeculectomy.
Argon Laser Trabeculoplasty (ALT)
In argon laser Trabeculoplasty, an argon laser makes tiny, evenly spaced burns in the trabecular meshwork. The laser does not create new drainage holes, but appears to stimulate the drain to function more effectively. The procedure is performed in an ophthalmologist's clinic with an eye drop anesthetic, and can usually be completed in 15-20 minutes. However, the total office time required is two to three hours. Eye pressure is monitored after surgery. A few people experience a rise in the eye pressure shortly after laser trabeculoplasty.
When attempts to increase the amount of fluid drainage from the eye through the trabecular meshwork fail, reducing the amount of fluid entering the eye is another option. Cyclophotoagulation is a procedure that uses a laser beam to treat parts of the ciliary body, located behind where the clear cornea meets the white of the eye. The ciliary body produces the aqueous humor. The destruction of parts of the ciliary body reduces production of this fluid, lowering eye pressure.
Cyclophotoagulation is generally used to treat advanced or aggressive open-angle glaucoma, and is usually used after treatments have been proven unsuccessful. The procedure, performed with a local anesthetic, can be painful postoperatively and medications for pain and inflammation may be necessary. Your ophthalmologist checks for inflammation and monitors the intraocular pressure in follow-up exams.
Risks associated with Cyclophotoagulation include pain, inflammation, and decreased vision for one to six weeks after the procedure. While the risks may sound unpleasant, people with severe glaucoma must reduce intraocular pressure or risk losing vision permanently.
Loss of vision can be prevented
Vision loss from glaucoma can be prevented if it is caught and treated in time. Glaucoma filtration surgery is effective in most people. Although complications may occur, most are treatable. While glaucoma treatments cannot restore vision already lost from glaucoma, early detection and treatment of glaucoma offers a better chance of preserving vision.