Surgical options for glaucoma are many

Studies show a number of new and alternative methods of treating glaucoma and lowering IOP.

Issue: February 15, 2002

Surgical options for glaucoma treatment are expanding in all directions. From newly approved laser technologies to effective ways of improving bleb filtration and aqueous flow, surgeons are exploring methods and technologies to reduce levels of intraocular pressure. Our Spotlight on Glaucoma Surgery in this issue explores many of these techniques through interviews with the procedures’ developers and practitioners.

SLT

The Selecta II laser (Lumenis) was approved for selective laser trabeculotherapy (SLT) by the Food and Drug Administration in 2001. According to Andrew G. Iwach, MD, the SLT lowers intraocular pressure (IOP) by producing short pulses of low energy light that target specific melanin-containing cells in the trabecular meshwork. In comparison with argon laser trabeculoplasty (ALT), Dr. Iwach said SLT is less traumatic to the eye and does not leave scars in the trabecular meshwork. Because of this advantage, SLT is a procedure that can be repeated.

Xe-Cl excimer

Another laser technology currently under investigation in Europe is the Xe-Cl excimer laser for glaucoma. The Xe-Cl laser uses a beam of UV radiation to increase aqueous flow by creating openings in the trabeculum and inner wall of Schlemm’s canal. In his experience with the technology, Philippe Sourdille, MD, noted that it produced significant reductions in IOP and need for glaucoma drugs with no serious complications. Data was accumulated from 47 patients in three centers. While initial results are promising, doctors recommend long-term follow-up to assess whether this treatment will warrant long-term use. The Xe-Cl excimer laser has not been approved in the United States.

Olivieri mask

Laser ablation in deep sclerectomy is safer and more precise with the use of the Olivieri mask, according to data presented by Ferdinando Romano, MD. The Olivieri mask is a device that consists of a small spatula with a triangular hole in the center. After the superficial flap is manually performed, the mask is positioned so that only a triangular portion of the sclera is exposed. This way, Dr. Romano said, surrounding tissue is preserved. The excimer laser will only ablate the triangular section of tissue in the mask. In the final stages of surgery, Dr. Romano suggests being cautious of the risk of deep ablation causing serious perforations.

Laser iridoplasty

Argon laser peripheral iridoplasty was found safe and effective for opening appositionally closed angles that remained closed after laser iridotomy. According to Celso Tello, MD, laser iridotomy is the “gold standard” for treating pupillary-block glaucoma. However, when laser iridotomy is contraindicated or cannot sufficiently widen the anterior chamber angle — due to the presence of mechanisms other than pupillary block — argon laser peripheral iridoplasty is an effective secondary procedure, Dr. Tello said. He noted that understanding the anatomic and pathophysiologic mechanisms involved in the etiology of various forms of angle closure are critical for diagnosis and management.

Viscocanalostomy

Another glaucoma surgical technique attracting attention recently is viscocanalostomy. In a study presented at the American Academy of Ophthalmology (AAO) meeting, surgeons were able to rupture the inner endothelial wall and provide a direct outflow of aqueous fluid, bypassing the trabecular meshwork. Developed by Robert Stegmann, MD, viscocanalostomy unroofs and dilates Schlemm’s canal. However, the procedure does not lower IOP as effectively as trabeculectomy, and therefore it is less desirable for some patients, investigators say.

5-FU

Nonfunctioning blebs can be restored to a level of adequate filtering through needling with application of the antimetabolite 5-fluorouracil (5-FU). Ming Zhao, MD, analyzed 34 patients retrospectively who received extensive needling and antimetabolite treatment after failed trabeculectomy. The retrospective study included patients from 1994 to 2000. In 86% of eyes, a mean IOP below 15 mm Hg was maintained with few or no postop medications needed. According to investigators, the dose of 5-FU did not correlate with the extent of IOP reduction obtained in the study; however, they said the agent is necessary and appropriate to retard fibrosis.

Antifibrotic agents – pros and cons

On the same subject, it appears the use of antimetabolite agents is still debatable. A recent debate at the AAO meeting found doctors in disagreement over the proper use of antifibrotic therapy. According to Stephen Obstbaum MD, the use of agents such as 5-FU in low-risk patients may result in additional complications, including endophthalmitis, suprachoroidal hemorrhage, hyphema or hypotony. Dr. Ostbaum suggested that only patients who have had previous conjunctival manipulation, who need drastically lowered IOP to protect optic nerves, who are at risk for bleb failure or who are Asian or black should be treated with antifibrotic agents.

In contrast, James Brandt, MD, said antifibrotic agents can be effective and beneficial to low-risk patients. According to Dr. Brandt, antifibrotic agents should be given according to the imminence of blindness. In fact, he said, long-term evaluations of drugs such as 5-FU have shown that cases of blindness associated with use of the agent are rare. In addition, he said application of antimetabolites has resulted in broadened bleb configurations.

Both Drs. Obstbaum and Brandt agreed that careful monitoring and patient selection are key when dealing with all antifibrotic agents.

CAT-152

Another agent, CAT-152, has shown promise in early European clinical trials. In a study led by David Broadway, MD, subconjunctival CAT-152 safely produced diffuse blebs. The CAT-152 agent acts as an antibody against transforming growth factor-beta2, thus preventing wound healing. However, according to Dr. Broadway, it is premature to draw final conclusions from the 6-month, follow-up study. A future study will include 2 years of patient monitoring and clear data on CAT-152 as an adjunct to phacotrabeculectomy, he said.

Management of bleb leaks

Conjunctival advancement was found to effectively treat late-onset filtering bleb leaks in a study presented by Donald L. Budenz, MD at the AAO meeting. Late-onset bleb leak repair is indicated in cases of shallow or flat anterior chamber, hypotony maculopathy, and a host of bleb-related infections. In his study, Dr. Budenz reported that only two patients out of 26 had recurrent or persistent leakage following conjunctival advancement after 19 months of follow-up. Dr. Budenz was pleased with initial results.

Scleral expansion bands

Finally, in a study published in Comprehensive Therapy, investigators found that scleral expansion bands effectively lowered IOP in patients with ocular hypertension or primary open-angle glaucoma.

Aaron W. Rifkind, MD, researched the effect of the scleral band on 21 patients and noticed that after 9 months of follow-up there were no signs of regression in IOP. In fact, there was an average IOP rate decrease of 7 mm Hg. Additionally, a majority of patients experienced improvements in visual acuity. Dr. Rifkind said the results compared favorably to results seen with glaucoma medications.