COAST TRIAL (Clarifying the Optimal Application of SLT Therapy)

 

The COAST trial seeks to compare the efficacy and safety of standard versus low energy primary selective laser trabeculoplasty (SLT) in eyes with mild-moderate primary open-angle glaucoma (POAG) or high-risk ocular hypertension (OHTN) and to determine the optimal interval and energy for repeat SLT.

At the 2018 annual meeting of the Association for Research in Vision and Ophthalmology (ARVO), Stephano Gandolfi presented a retrospective study of his patients at the University of Parma, Italy, in which a regimen of low-energy SLT repeated annually irrespective of intraocular pressure (IOP) produced significantly longer medication-free survival than standard SLT repeated as needed, in patients with POAG or OHTN.

In Gandolfi’s study, newly-diagnosed POAG eyes were treated primarily either with ALT 360° performed once, standard SLT 360° repeated as needed at standard energy, and low-energy 360° SLT (0.4 mJ/spot x 50-60 spots) repeated annually at low energy regardless of IOP.

After 10 years of follow-up, medication-free rates were 22.6% in the ALT group, 25.0% in the standard SLT group, and 58.3% in the low-energy SLT group (p<0.001).

Gandolfi’s data suggested that the long-term utility of SLT in glaucoma management can be improved by altering the energy level and frequency at which SLT is performed.

The National Eye Institute (NEI) is conducting randomized multicenter trials based on the above observations. These trials—collectively named the Clarifying the Optimal Application of SLT Therapy (COAST) trial—were funded in late 2020 by NEI to compare standard versus low-energy primary SLT and annual versus pro re nata (PRN) repeat SLT and are currently in the pre-enrollment phase.

The COAST Trial- based on Gandolfi’s proof-of-concept study and evidence-based biological plausibility—that low energy SLT, repeated annually irrespective of IOP, may reduce both SLT-related and glaucoma-related cumulative TM damage, thus preserving TM responsivity to SLT and extending the duration of which SLT can maintain glaucoma control and prevent or delay the need for medications or surgery.

This trial can bring a paradigm shift in the management of such cases, reducing the burden of medications and still preserving IOP levels.