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Surgery not always a last resort for glaucoma patients

Issue: February 1999

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Therapeutic management of glaucoma to reduce intraocular pressure (IOP) will sufficiently slow the visual field loss and optic nerve damage in most patients. In patients for whom drugs are no longer an option — either because of ineffectiveness or toxicity — the next step is usually laser treatment. Some practitioners are now even considering laser treatment of glaucoma earlier in the management of the disease.

For some patients, especially those with open-angle glaucoma, laser treatment will offer relief for only a few years, requiring either retreatment or incisional surgery to bring the patient’s IOP under control.

When to consider surgery

Determining when to progress from medication to laser treatment will vary from patient to patient, said J. James Thimons, OD, in private practice in Fairfield, Conn., and former director of the Glaucoma Institute at the State University of New York College of Optometry.

“You set a goal pressure that is consistent with the patient’s glaucomatous presentation: the cup-to-disc ratios, present field damage, current pressure, the patient’s general health and predisposing factors such as age, race and refractive error. You consider all those elements and you put in place a reasonable goal that he or she needs to maintain to be comfortable,” Dr. Thimons said.

If the patient cannot achieve this IOP after a few months and after using several different medications, then laser treatment should be considered, he said.

“If you don’t feel you’re getting where you need to be and the patient is at risk, or you show clear demonstrated evidence of progressive disease, then I think it is perfectly appropriate to recommend laser treatment right away,” Dr. Thimons said.

Even in patients who are stable with medication, there is the chance that systemic complications could develop or the patient could develop a sensitivity to the drug or a reaction to preservatives in the drops that would require the practitioner to consider moving on to laser intervention, he said.

Another consideration in determining when to recommend surgery is progression over time, said Alan S. Crandall, MD, who practices at the John Moran Eye Center in Salt Lake City.

“It is necessary to know what the patient was like 1, 2 and 3 years ago,” Dr. Crandall said. “Then, you need to determine the cause of the change. Is the patient noncompliant? Are the medicines not appropriate and a simple change in medicine would be likely to bring him or her into a safe zone? Are other things involved such as high blood pressure or diabetes — things that might be outside the realm of the eye that could be affecting the decision as well?”

Don’t save the laser for last

Once the nature of the disease is understood, certain specific conditions may indicate that laser treatment or incisional surgery is appropriate as a primary therapy, Dr. Crandall said. Black patients with a lot of pigment and patients with pseudoexfoliation or pigmentary dispersion syndrome are likely to do well with argon laser trabeculoplasty (ALT). If a patient presents with IOP in the mid-20s or low-30s and has a cup-to-disc ratio of 0.7 or 0.8, the practitioner does not have the time to try a series of medications or wait and see if laser treatment will lower the pressure enough. Significant damage has already occurred, so incisional surgery might be recommended, Dr. Crandall said. The traditional approach of trying different medications, then implementing laser therapy and finally relying on incisional surgery is no longer considered the best course of action for every patient.

“You must individualize the therapy to each patient’s optic nerve and his or her socioeconomic situation — can he or she afford the drops, will he or she use them if they’re prescribed — and make the determination based on what’s in the best interest of the patient,” Dr. Crandall said.

Laser treatment should be considered as an early option in glaucoma management, according to Richard A. Lewis, MD, in practice in Sacramento, Calif.

“I find laser surgery to be most effective in the early stages of glaucoma when you are seeing field loss and cupping, but not to a severe extent in which patients’ pressures are elevated,” Dr. Lewis said.

“I often consider laser therapy to be just another form of medical therapy. It’s not as definitive as surgical therapy, as it does not get patients off their eye drops. It does work and has been shown to be effective, but it seems to wear off over time. In a patient who has well-defined, advanced disease, I’d rather go to a surgical approach that definitively gets his or her pressures down and gets him or her off eye drops,” he added.

There are some conditions where laser treatment is the primary choice, such as pseudoexfoliation syndrome and narrow-angle glaucoma, Dr. Thimons said.

ALT treatment

The type of laser treatment depends primarily on the nature of the glaucoma. Most patients with primary open-angle glaucoma will undergo ALT, where the trabeculum receives 50 to 60 treatments across 180°, Dr. Thimons said. The energy level of the laser is generally between 500 and 1,000 mW, depending on the skin pigment, the pigment of the trabeculum and the amount of material in the anterior chamber.

The mechanical theory behind this approach is that the laser shrinks parts of the trabecular meshwork, stretching the tissue around the burn, which opens adjacent spaces and increases outflow, Dr. Thimons said.

“About 20% to 25% of patients are still doing well at 5 years with only laser treatment,” he said. “That’s a high failure rate, but, from my perspective, that’s a procedure that deserves a much earlier position in the overall armamentarium. I have many patients for whom chemicals are hard to take because of side effects, and I no longer wait nearly as long to recommend laser therapy.”

The age of the patient also plays a role when considering laser treatment, Dr. Thimons said. Because of the limited duration of the results of ALT, the procedure is better suited to older patients.

“It’s not a very good match when the patient is 22, because, typically, the effect begins to diminish somewhere between the second and fifth year,” he said. “If you’re dealing with a 22-year-old, you’re dealing with a little window of his or her long-term disease. If you’re treating a 75-year-old, you’re realistically looking at some substantial percentage of the remainder of his or her life.”

Laser iridotomy

A different laser procedure, laser iridotomy (LI), is appropriate for patients with closed-angle glaucoma. In an LI, a laser is used to create a communication between the anterior and posterior compartments of the anterior chamber. Previously, this was performed using an argon laser, but that method had limitations, such as the patient’s skin color, the thickness and amount of pigment in the iris and a number of other factors, Dr. Thimons said. This has been replaced by the Nd:YAG, which usually perforates the iris on the initial treatment; the argon could take 40 to 80 hits to achieve communication.

Another advantage of the Nd:YAG is that irises treated with this laser rarely re-close spontaneously, while irises treated with an argon laser will have pigment grow back over the treatment area in 30% to 50% of patients, Dr. Thimons said. This puts the patient back at risk for the initial condition.

Unlike ALT, “iridotomy is a pretty definitive cure for an acute angle-closure glaucoma where the effect lasts indefinitely,” Dr. Lewis said.

Laser iridoplasty

An intermediate procedure that may be necessary before either ALT or LI is laser iridoplasty, which reconfigures the iris anatomy to allow for the use of another technique, Dr. Thimons said. In this procedure, the laser uses less energy — about 200 mW, compared to 500 mW — and a wider band to shrink iris tissue away from the angle, which will allow another type of treatment.

This may be necessary before ALT, if there is no clear view, or prior to LI to clear the iris from the endothelial surface and avoid damage to the cornea.

Holmium laser sclerostomy

Holmium laser sclerostomy is an established procedure that has not met with universal acceptance due to what many perceive as a higher incidence of complications, Dr. Thimons said. In this operation, a holmium laser is used to perforate the trabecular meshwork through the sclera, creating a hole that gives the aqueous a direct passage out of the chamber.

The theoretical advantage to this approach is that the globe is never incised, and some practitioners like the idea of a less invasive approach, Dr. Thimons said. The downside is a relatively high failure rate and the likelihood of complications with closure and inflammation.

Incisional treatment

If laser therapy is not successful in reducing the IOP, the next step has generally been incisional surgery. While there is a structured approach to glaucoma management, practitioners should take individual considerations — such as systemic health, complications from the disease and extent of the disease — into account when developing a treatment plan for each patient, Dr. Thimons said.

The most common incisional approach is trabeculectomy, where tissue from the sclera and trabecular meshwork is removed and a filtering bleb is created to drain aqueous. Within the past 5 to 8 years, the success rate of this procedure has increased from between 50% and 60% to 85% to 90% with the advent of the antimetabolite drugs 5-fluorouracil (5-FU) and mitomycin C, which prevent scarring, Dr. Thimons said. Unlike other surgeries, the wound healing response undermines the effectiveness of the procedure.

“Because of mitomycin and 5-FU, it’s so much easier to justify a surgical intervention because the success rate is so much higher. Previously, trabeculectomies didn’t work that well, and you needed virgin or primary tissue,” Dr. Thimons said.

Not all patients will be treated with antimetabolites, Dr. Crandall said. Young myopes have a high incidence of hypotonous maculopathy and should not be treated with mitomycin, though 5-FU might be used. Elderly patients and patients with AIDS who are poor healers would not need the drug. On the other hand, secondary glaucoma patients almost always require the use of antimetabolites.

Viscocanalostomy

Viscocanalostomy is a new technique gaining acceptance in the United States after an enthusiastic reception internationally. Viscocanalostomy was developed by Robert Stegmann, MD, of the Medical University of Southern Africa, Medunsa, Dr. Crandall said. In the short term, the procedure has shown good results, he added.

In this procedure, the surgeon dissects down through the sclera to unroof Schlemm’s canal, then floods Healon GV (sodium hyaluronate, Pharmacia & Upjohn) into the trabecular meshwork to open the meshwork and re-establish the natural flow.

Drainage implants

---One day postop: After undergoing the deep sclerectomy and wick implant, the patient should present with a diffuse filtering bleb in a quiet eye with a deep anterior chamber.

There are a wide variety of devices that can be sutured into the anterior chamber to provide drainage out of the chamber into the subconjunctival space where it is spread out over a large plate that functions as a diffusion device. Without the plate, the drainage would not be as great because the fluid would not be spread out over a large enough area, and eventually the subconjunctival tissue would probably scar over the implant, Dr. Thimons said.

The implants are generally used after an initial surgical procedure has failed or if the patient presents with uveitic, neovascular or traumatic glaucoma where there is damage to the trabecular meshwork, or if the rapid healing prevents formation of a filtering bleb.

Implants are generally not used as a primary surgical treatment because, while they do provide a consistent lower pressure, they do not lower the IOP as much as a successful trabeculectomy, Dr. Thimons said. On the other hand, the effects of implants tend to be more long lasting, while trabeculectomies provide low pressures initially, but the IOP tends to rise over time.

Wick implant

---Sclerectomy with collagen wick implant: The implant was placed radially in deep sclerectomy dissection.

Another surgical approach is the use of a wick (STAAR Surgical Co., Monrovia, Calif.). The wick has not been used extensively, but has been endorsed by those who have used it, Dr. Thimons said.

It is a 2.5-mm x 0.5-mm cylinder composed of a biocompatible, copolymer collagen material designed to remain in place for 6 to 9 months after being implanted following a deep sclerectomy. A Food and Drug Administration clinical trial is underway in the United States for this treatment, Dr. Crandall said.

During the postoperative period, the wick serves as a mechanism to maintain the fluid channel to the subconjunctival space, which allows for more successful long-term healing with less exposure, Dr. Thimons said.

Cyclodestructive procedures

As a last resort in glaucoma management, there also are operations in which part of the ciliary body (where the aqueous is formed) is destroyed, Dr. Thimons said. This is frequently performed using a cryosystem or, more recently, a deep-focus YAG laser.

A number of complications have occurred with these approaches, including unpredictable visual loss as a result of macular edema, making this desirable only as a last option.

Postop care

Following laser surgery, patients are generally returned to their optometrists’ care the next day, Dr. Thimons. Post-incisional surgery care is more complex, and the patient frequently remains with the ophthalmologist for several weeks until the eye has stabilized. Typically, the glaucoma surgeon will handle follow-up care for a minimum of 1 to 2 weeks, covering at least two or three visits, he said.

Dr. Crandall sees postop glaucoma patients on days 1 and 3, then weekly until the patient has stabilized. In these exams, he looks for shallow chambers, leaks, sutures that need laser treatment to prevent them from sealing and Tenon’s cysts that would need to be incised.

This period is critical to the success of the surgery, Dr. Lewis said.

“The key to success is the management of the postoperative patient — that’s what makes the surgery work. It’s when you massage, laser the sutures, intervene with certain drops and not intervene — all of which is dependent on clinical judgment,” Dr. Lewis said.

When the patient does return to the care of the OD, the care regimen should be more intensive than that of a nonsurgical glaucoma patient because of the added risks of developing infection, a bleb leak and cataract formation, Dr. Lewis said. Patients who are stable should be seen at least twice a year, he said.

Patients also should realize that the mechanism of glaucoma has not changed as a result of surgery, Dr. Thimons said.

“Typically, after successful surgery, medication is minimized or absent. However, after a year or two, patients may start back up the trail of medical therapy,” he said.

For Your Information:

• J. James Thimons, OD, is a charter member of the Primary Care Optometry News Editorial Board and can be contacted at Ophthalmic Consultants of Connecticut, 165 Stella Lane, Fairfield, CT 06432; (203) 255-6196; fax: (203) 254-1467. Dr. Thimons has no direct financial interest in the products mentioned in this article nor is he a paid consultant for any companies mentioned.
• Alan S. Crandall, MD, can be reached at the John Moran Eye Center, 50 N. Medical Dr., Salt Lake City, UT 84132; (801) 581-2769; fax: (801) 581-3357. Dr. Crandall has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• Richard A. Lewis, MD, can be reached at 3939 J St., Sacramento, CA 95819; (916) 455-9938; fax: (916) 451-1953; e-mail: rlewismd@pacbell.net. Dr. Lewis did not disclose if he has a direct financial interest in the products mentioned in this article or if he is a paid consultant for any companies mentioned.