Physicians are using the procedure to treat various stages of the disease.
Reviewed by Yasemin Sozeri, MD
Laser trabeculoplasty can be used to treat various stages of glaucoma but, interestingly, the best way to apply it is still being debated.
Yasemin Sozeri, MD, discussed the procedure’s role in the management of glaucoma and the major clinical trials being conducted in this area at the Cleveland Eye Bank Virtual Vision Research Symposium. Sozeri is an assistant professor in the Department of Ophthalmology and Visual Sciences and a staff member at the University Hospitals Eye Institute of Case Western Reserve University School of Medicine, in Cleveland.
There are currently 3 theories regarding the mechanism of action of laser trabeculoplasty. The mechanical theory suggests that the laser creates thermal changes that lead to contraction of the trabecular meshwork and the opening of adjacent spaces, thus increasing aqueous flow and lowering IOP. The cellular theory postulates that it causes trabecular meshwork cells to divide and repopulate the meshwork. And the biochemical theory, the most popular, propounds that the laser increases chemical mediators that bring about a remodeling of the meshwork, Sozeri said.
Argon laser trabeculoplasty (ALT), initially the go-to procedure, was later replaced in large part by selective laser trabeculoplasty (SLT), using a YAG diode laser.
The principal outcome of the AGIS study, one of the earliest trials to evaluate ALT in advanced glaucoma, was that the treatment remained successful after 10 years in about 50% of patients, irrespective of race.
The Glaucoma Laser Trial evaluated laser trabeculoplasty versus timolol in newly diagnosed glaucoma. Two-year results showed that in the medication arm IOP was about 2 mm Hg higher than in the laser arm; longer-term evaluation showed that IOP was controlled in approximately 40% of patients without medication or with 1 medication and in 15% of those receiving only 1 medication.
Studies performed in the 1990s evaluated SLT, which targeted the pigment cells in the trabecular meshwork, versus the application of large thermal burns evaluated in previous trials.
Trials comparing ALT and SLT showed comparable IOP-lowering effects but less inflammation in SLT patients. SLT also seemed to be more beneficial for patients undergoing second laser treatments.
The 3-year LiGHT trial (NCT03395535) compared SLT to prostaglandin analog eye drops in primary open-angle glaucoma and ocular hypertension. The results showed that in the SLT arm, the IOP of over 90% of patients was controlled without medication or with only 1 medication, whereas in the in eye drops arm, the IOP of only 67% of patients was controlled. “It was most remarkable,” Sozeri commented, “that the SLT-treated patients needed fewer glaucoma surgery over the course of the study and the costs were lower for patients.”
The SALT trial (NCT00981435) evaluated the effectiveness of perioperative anti-inflammatory drops instilled after laser trabeculoplasty and found a slightly greater IOP decrease at 12 weeks compared with placebo drops. However, this study had a number of limitations, including short duration, small sample, higher preoperative IOPs in patients who received anti-inflammatory than in those who received placebo, and a greater number of patients who underwent 360-degree trabeculoplasty compared with those in the placebo group.
The COAST study (NCT04967989), a new randomized, controlled trial, is being conducted to determine the optimal application interval and energy level of the SLT laser and repeated SLT treatment. The trial will enroll more than 635 patients who will be treated with standard-dose SLT or low-dose SLT. The investigators will compare outcomes at 12 months, and patients will be re-randomized to undergo as-needed SLT at the original dose or annually at the low dose. Outcomes at 48 months will then be analyzed, Sozeri reported.
The GLAUrious trial (NCT04758598) is enrolling patients and will evaluate a novel system that will apply laser to 360 degrees of the trabecular meshwork through the limbus without a contact lens for 2 seconds compared with the standard 90 or 120 seconds required for 360-degree treatment.
“This is an exciting way that we may be able to optimize SLT treatment even further,” Sozeri stated, adding that laser trabeculoplasty “is a disease-modifying treatment, and there are cost-savings for both the patient and the health care system. We currently are working on the best ways to apply SLT.”