Micropulse laser approach seems safe, effective for trabeculoplasty

January 15, 2008

Micropulse laser trabeculoplasty (MLT) using a specific diode laser seems to be a safe and effective approach to performing trabeculoplasty.

Key Points

In a pilot study that compared MLT and selective laser trabeculoplasty (SLT), evaluations at 3 months postoperatively showed that IOP decreased from the baseline in both procedures, he said. The results indicated that MLT, which uses higher energy levels, smaller spot sizes, and shorter exposure times than SLT, was well tolerated, with no laser flashes, intraoperative discomfort, or postoperative pain. The eyes were "quiet," with negligible postoperative cell and flare reaction.

Dr. Lewis, who is in private practice in Sacramento, CA, provided a case report of a 74-year-old black woman with an 8-year history of glaucoma. Her highest IOP was 24 mm Hg. The treatment protocol was complicated by dry eyes and chronic irritation; the patient received punctal plugs for dry eye. Her medical history was positive for arthritis, hypertension, and asthma.

"This is an overwhelming and expensive list of medications and not unusual in a patient with glaucoma. It is a sad statement of how we are trying to manage a disease that will progress despite these treatments," Dr. Lewis stated.

Visual acuity was 20/40 and 20/60 in the right and left eyes, respectively. The left eye had an afferent pupillary defect. Cataracts developed bilaterally. The inferior cornea was stained despite the punctal plugs. The cornea was thin, with pachymetry measurements of 438 and 452 B5m, respectively. The IOP values were 24 mm Hg and 23 mm Hg in the right and left eyes, respectively. The open angle was grade 4 on gonioscopy, with large cupping.

"The diagnosis of glaucoma is not in question here, but rather what is the best treatment approach for this patient, who is taking a substantial number of medications," Dr. Lewis said. "Ophthalmologists who treat patients with glaucoma can certainly appreciate this patient's situation."

Options limited

When considering managing glaucoma in a patient such as this, Dr. Lewis said that options had been very limited. "Surgery remains a very complicated process with numerous long-term problems. Argon laser trabeculoplasty was introduced in the early 1980s. Over the years, the argon laser has been supplanted by the diode laser. More recently, SLT and now MLT have provided a means to lower IOP with invasive surgery or drops," he said.

Dr. Lewis said he has been using the aforementioned diode laser for about 6 months. He described it as a much simpler device than the argon laser and said it has multiple uses for treating glaucoma, specifically, laser trabeculoplasty, cyclophotocoagulation, and laser suture lysis. The device has a slit-lamp adapter and special attachment for the G-probe.

Trabeculoplasty is performed in the preset micropulse mode (810 nm). The only parameter the surgeon has to control is the spot size, Dr. Lewis said.

"In some cases in which I have not achieved the results I wanted, the spot size can be decreased to obtain the desired effect because the power cannot be increased." he added.

Generally, successful laser trabeculoplasty procedures have similar outcomes, resulting in a decrease in IOP of 20% to 30%. The long-term effect can be limited, with a stable IOP decrease maintained for 3 to 24 months, according to Dr. Lewis.