Laser options are on the rise for glaucoma treatment

Selective laser trabeculotherapy and endoscopic cyclophotocoagulation provide competition for ALT.

ByRochelle Nataloni

BALTIMORE — Although drugs remain the first-line treatment for most glaucoma patients, many glaucoma specialists agree that laser surgery can work as first-line therapy in a significant number of their patients. Argon laser trabeculoplasty (ALT) is considered conventional therapy, and rare is the glaucoma surgeon whose armamentarium lacks an argon laser.

“It was the glaucoma surgeons with trabeculoplasty, not the refractive or retinal surgeons, who were the first to really revolutionize laser treatment for the ophthalmologist,” said Alan L Robin, MD. “Now it’s time to ask, ‘What’s next? What is the next generation of laser therapy?’”

Selective treatment

---Endoscopic probe allows laser treatment of ciliary processes under direct observation.

Selective laser trabeculotherapy (SLT) is one possible answer. The procedure appears to be an effective way to lower intraocular pressure in open-angle glaucoma patients who are on maximum medical therapy or who have failed previous ALT attempts.

“The procedure was designed to be an improvement over ALT in that it causes less structural damage to the trabecular meshwork, since there are no coagulation effects. But we’re finding that it may be somewhat complementary to ALT in that it can be used either before and definitely following ALT,” said Mark Latina, MD, who developed the procedure.

Formerly called selective laser trabeculoplasty, SLT relies on a process called selective photothermolysis, which targets melanin granules within the cell. Following SLT, the melanin granule is disrupted resulting in cell death.

SLT applies a q-switched frequency doubled Nd:YAG laser (Selecta 7000; Coherent Medical Group, Santa Clara, U.S.A.), which uses a wavelength of 532 nm. The spot size is 400 µm, which spans the entire height of the trabecular meshwork, as opposed to the 50 µm spot size used with ALT. The wavelength selectively targets pigmented trabecular meshwork cells without causing structural or coagulative damage to the meshwork. “The idea with SLT is basically to eliminate the scarring, which we know causes reduced flow,” Dr. Latina said, “and we know that if we perform ALT too many times, the pressure goes up.”

Not a replacement

But Dr. Latina is not suggesting that SLT will replace ALT. He sees the two procedures being used in a “synergistic or complementary way,” he said. “Most glaucoma specialists already have an argon laser or have access to one, but the argon laser doesn’t always work.... Although I would use SLT as a first line before argon laser, it might not necessarily replace it such that we would never use argon laser again,” he said.

Endoscopic approach

Martin Uram, MD, said the problem with glaucoma procedures performed at the slit lamp with a laser is that they work for some forms of glaucoma, but not the more severe cases, and not in certain types of glaucoma at all. With endoscopic cyclophotocoagulation (ECP), however, which Dr. Uram developed for glaucoma management, he said it does not matter why the patient has glaucoma or how severe it is.

The aim of ECP is to decrease the amount of fluid produced in the eye, rather than to increase its outflow as in more conventional therapies. Dr. Uram treats the ciliary body using an 810 nm diode laser. “The technology is all in the same box. All you need for endoscopy is a laser, a video camera at the end of the laser probe and a light source,” he said. Dr. Uram estimates that more than 10,000 ECP procedures have been performed to date, mostly in the United States.

“All the techniques throughout history that have addressed the ciliary body have been blind techniques — you guess where the ciliary body is, and you do something through the eye wall that you think is affecting your target tissue. So we developed an endoscope that you can put inside the eye enabling the surgeon to see the ciliary processes, which is where the cells are that make the fluid,” Dr. Uram said. “The problem with the blind approach is that because you can’t see your treatment area, you damage other areas — you laser parts of the iris, parts of the retina — things that have nothing to do with the production of fluid in the eye. You get overtreatments and undertreatments, and that creates the complications that are associated with the transscleral approach.

“Because you can see clearly what you’re doing with ECP, you can control very precisely the tissue effect of the treatment, which results in far fewer overtreatments and undertreatments,” he said. The incidence of overtreatment is less than 1%, according to Dr. Uram. Incidence of re-treatment depends on the mechanism of glaucoma, with an average of about 12% to 15%, he said.

Once considered controversial and still described by most as invasive, ECP is particularly effective in combination with cataract surgery. “If you have someone who is not doing well on drops, or you have someone who you’re going to be inside their eye anyway — such as a cataract patient who has glaucoma — it is not high risk, it is low risk. The controversy comes because there is no general agreement in the glaucoma community about when to do surgery and when not to.”

The biggest problem with ECP, according to Dr. Uram, is that novices tend to take a conservative course and they do not laser enough of the ciliary body. “Then it doesn’t work very well, because they didn’t do enough,” he said.

Dr. Uram said most of the controversy regarding ECP was removed when Jorge A. Alvarado, MD, performed a study using ECP to treat refractory glaucoma and achieved a 90% success rate. Dr. Alvarado and colleagues from the Department of Ophthalmology, University of California, San Francisco, reported [Am J Ophthalmol. 1997;124:787-796.] that “retrospective analysis over the mean follow-up period of 13 months suggests that endoscopic cyclophotocoagulation has a higher success rate than transscleral cyclodestructive approaches do.”

“One of the beauties of ECP,” Dr. Uram said, “is that a surgeon who has very little experience in glaucoma surgery — let alone in the more difficult intractable glaucoma cases — can treat the worst cases of glaucoma because there isn’t that much difference technically between performing a simple case versus a difficult case.”

For Your Information:

Mark Latina, MD, can be reached at 20 Pond Meadow Drive, Ste. 204, Reading, MA 01867 U.S.A.; +(1) 781-942-9876; fax: +(1) 781-942-9877. Dr. Latina has a direct financial interest in SLT. He is a paid consultant for Coherent Inc.

Alan L. Robin, MD, can be reached at 6115 Falls Road, 3rd Floor, Baltimore, MD 21209-2226 U.S.A.; +(1) 410-377-2422; fax: +(1) 410-377-7960. Dr. Robin did not participate in the final preparation of this article.

Martin Uram, MD, can be reached at EndoOptiks, 39 Sycamore Ave., Little Silver, NJ 07739 U.S.A.; +(1) 732-530-6762; fax: +(1) 732-530-3837. Dr. Uram has a direct financial interest in ECP. He is not a paid consultant for any companies mentioned.

For reprints of the study by Jorge Alvarado, MD, contact Janet Chen, MD, at fax: +(1) 415-476-0336.