Researchers are preparing to launch a clinical trial that may change the way we treat milder forms of glaucoma and free patients from daily drops. The Clarifying the Optimal Application of SLT Therapy, or COAST, trial will compare the efficacy and safety of standard and low-energy SLT to determine optimal treatment intervals and energy levels for repeat SLT.1
SLT is a safe and effective way of lowering intraocular pressure in patients with mild to moderate glaucoma by targeting pigmented chromophores in the trabecular meshwork. It can be used at any point in the glaucoma treatment paradigm, though it’s most effective as a first-line treatment. Acceptance of SLT as a primary therapy picked up after the publication of the Laser in Glaucoma and ocular Hypertension Trial (LiGHT) in 2019, which demonstrated that primary SLT was at least as effective as medical therapy in treatment-naïve patients with mild to moderate disease.2 At the three-year mark in the trial, the SLT and medication groups had a similar mean IOP, but the medication group experienced more disease progression (10% vs. 6.4%), and all 11 trabeculectomy procedures in the study occurred in the medication group.
The standard of care for SLT involves performing the treatment and waiting for its effects to wear off. “We wait for whatever impairs the tissue to increase the pressure again,” says lead researcher Tony Realini, MD, MPH, of West Virginia University. “Then, we’re back in a position where we have to rescue the tissue and get it to work again.”
Evidence in the literature suggests that there’s a limited number of rescue cycles an eye can go through before tissue stops responding. “That’s when patients have to go on medical therapy, which is known to have high rates of poor adherence. Our hypothesis is that low-energy SLT performed annually will do less damage to the trabecular meshwork than standard-energy SLT performed pro re nata. So, right off the bat, the meshwork will be healthier after low energy than standard.”
This approach should sound familiar—it’s akin to the treat-and-extend paradigm used now in place of PRN treatment for AMD. The retina world transitioned to this now standard-of-care practice after it found that anti-VEGF was losing its efficacy with each subsequent rescue injection, until there was no further benefit. Now, retina specialists try to find the longest interval in which a particular eye doesn’t deteriorate, and then continue treating along those lines.
Encouraged by the LiGHT trial results, and inspired by low-energy SLT research conducted by Dr. Gandolfi in Italy, Dr. Realini and his colleagues have begun work on the COAST trial, which received more than $15 million dollars in funding from the National Eye Institute and National Institutes of Health.3
The COAST trial will look specifically at newly-diagnosed, treatment-naïve patients with mild or moderate primary open-angle glaucoma or high-risk ocular hypertension. The investigators hope to determine whether retreatment should be done when the laser effect wears off or annually at lower energy levels to keep the pressure down. The multicenter trial aims to enroll more than 600 patients from around the world.
“We may be able to treat a patient with initial laser to start, and then every year very gently ‘top them up’ to keep the trabecular meshwork healthy. We may get a more powerful, longer effect from SLT this way,” says study investigator Gus Gazzard, MD, FRCOphth, of Moorfields Eye Hospital and University College London. “It could transform the way we do laser.”
“The goal is to have drop-free therapy for patients,” says Dr. Realini. “Poor adherence is a major contributing factor to loss of vision in glaucoma. We want to move glaucoma therapy away from patient-administered topical eye drops.”
Results are expected in another three years or so, Dr. Realini says. Visit www.coasttrial.org to follow the study’s progress.
1. Realini T, Gazzard G, Latina M, eta al. Low-energy selective laser trabeculoplasty repeated annually: rationale for the COAST trial. J Glaucoma. 2021;30:545-51.
2. Gazzard G, Konstantakapoulou E, Garway-Heath D, et al. Selective laser trabeculoplasty versus eye drops for first-line treatment of ocular hypertension and glaucoma (LiGHT): a multicenter randomized controlled trial. Lancet. 2019;393:1505-16.
3. Gandolfi S. Low power selective laser trabeculoplasty (SLT) repeated yearly as primary treatment in open angle glaucoma(s): long term comparison with conventional SLT and ALT. E-Abstract 3459. Association for Research in Vision and Ophthalmology Annual Meeting; May 1, 2018; Honolulu, HA.