Eyeworld

EW GLAUCOMA 80 by Maxine Lipner Senior EyeWorld Contributing Editor Laser trabeculoplasty treatment by the letter The latest on what to expect from varying laser trabeculoplasty options I t's often par for the course with open-angle glaucoma patients' use of laser trabeculoplasty. For patients it's a quick, pain-free option that may help to allevi- ate the need for drops. There's a whole alphabet soup of approaches —ALT (argon laser trabeculoplasty), SLT (selective laser trabeculoplasty), and MLT (micropulse laser trabecu- loplasty). But of course not all laser trabeculoplasty is equal, or is it? Here's what EyeWorld found. SLT vs. ALT For some time, practitioners have been weighing how SLT, the relative newcomer, stacks up against the more traditional ALT, which has been around for decades. Paul L. Krawitz, M.D., assistant clinical pro- fessor of ophthalmology, Columbia University College of Physicians and Surgeons, New York, has used both treatments in his practice. While both supply energy to the trabecular meshwork, they work in different ways. "ALT is visible light that interacts with the pigment that's in the trabecular meshwork and actually causes a tiny burn," Dr. Krawitz said. "Selective laser trabecu- loplasty, called a Q-switched YAG laser, applies energy that's invisible." Both apply energy to the trabecular meshwork, which filters aqueous and lowers pressure. "The difference functionally is that the argon laser, because it causes a small burn, phys- ically destroys a small portion of the trabecular meshwork," Dr. Krawitz said. While both are equally effective in studies, Dr. Krawitz sees a key dif- ference between the two. "Argon laser trabeculoplasty, because it causes physical damage to the tra- becular meshwork, can't be repeated ad infinitum, if the pressure starts rising in a couple of years," he said. With ALT, practitioners can actually witness the burn to the trabecular meshwork, which paradoxically is a sign that the argon spot has been successfully applied. Dr. Krawitz finds that he can re- peat the SLT procedure with his Lumenis laser (Santa Clara, Calif.) several times—something that com- pletely changes the treatment algo- rithm as a result, in a disease that currently practitioners hope to con- trol at best. "The issue with argon laser trabeculoplasty is that you run out of bullets," Dr. Krawitz said. "You can do it once and get a lot of mileage, the second time gets a little less mileage, and then you have to look for an alternative way of con- trolling pressure." Meanwhile, he finds that SLT can be redone. "Although on a first- time basis SLT has an equivalent re- sult, you know that 2-4 years later, should the patient's pressure elevate again you can come back to tissue that has not been destroyed by heat burns and reapply energy," Dr. Krawitz said. "It puts a lot more bul- lets in your gun to maintain the pa- tient's pressure." Initial outcomes with ALT and SLT are roughly equivalent. "In the literature they both have about an 80% success rate at reducing pres- sure in a meaningful way," Dr. Krawitz said. In his hands, he finds that his numbers for ALT are about a 70-75% success rate and up to 88% for SLT. The pressure reduction is about 20%. Adding MLT to the mix Adam J. Lish, M.D., attending in ophthalmology, Mount Sinai Med- ical Center, New York University, New York, has in the past used ALT. However, instead of turning to SLT when he needed a new laser, he opted for MLT with the IQ 810 (Iridex Corp., Mountain View, Calif.). "As a glaucoma specialist I was looking for a laser to replace my argon laser," Dr. Lish said. "My in- terest in diode lasers started when I was a fellow back in the early 90s, and I was well aware that diode did the job; also, my retina specialist used an iris diode laser to do his work." That led Dr. Lish to MLT, which makes use of the diode technology. "It does as good a job clinically as ALT and SLT and does not cause scarring like ALT," Dr. Lish said. One of the other things that drew him to the MLT laser was the fact that, un- like SLT, it could do a variety of things. "Even in a glaucoma spe- cialty office there are other things that you need to do with the laser," Dr. Lish said. In addition to trabecu- loplasty, he found that the MLT laser could do iridoplasty, cut sutures, and perform laser iridectomy. He also felt that it was more financially respon- sible since the laser cost about 40% less than an SLT laser and could serve a variety of purposes. Outcomes with MLT are equiva- lent to ALT, Dr. Lish finds. There was no scarring involved with the tech- nique. With MLT technology the diode laser emits a train of short pulses in- stead of one continuous one, accord- ing to Giorgio Dorin, Ph.D., director of clinical application and develop- ment, Iridex. With these short pulses, the tissue has a chance to cool between shots, and the thermal February 2011 September 2011 Multiple spots in the placement of the argon laser in the trabecular meshwork. With ALT, practi- tioners see the burn to the trabecular meshwork, which is a sign the spot has been successfully applied Source: Richard A. Lewis, M.D.

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