Prostaglandin Pretreatment Provides No Added Benefit Before SLT, Study Says

A new UK retrospective study found that SLT achieves comparableIOP reduction whether used as first-line therapy or after prostaglandin analog treatment. Although prostaglandin plus beta-blocker therapy produced greater initial IOP lowering, pretreatment offered no significant advantage before SLT, supporting guideline-based early laser use in appropriate patients. Photo: Nate Lighthizer, OD. Click image to enlarge. In the treatment of glaucoma, selective laser trabeculoplasty (SLT) is a well-recognized first-line treatment; however, some clinicians still opt for offering prostaglandin analog (PGA) drops initially and SLT as an adjunct. A group of researchers from the United Kingdom analyzed whether this method made a difference in outcomes, and ultimately determined that SLT was generally less effective when used in conjunction with prior drop treatment, particularly with PGA alone, presumably because of the lower baseline IOP prior to laser therapy in patients already treated with topical agents. This same research group conducted a new study to evaluate the efficacy of various topical antihypertensive medications prior to SLT, the results of which were recently published in the journal Eye, and found no significant difference in the overall reduction in intraocular pressure (IOP) between eyes treated with PGA prior to SLT and those that received SLT only. The study authors conducted this retrospective review using data from the Lancashire Teaching Hospitals Trust, part of the UK’s National Health Service. The average age was 72 years and subjects were equally split between men and women. Out of 196 eyes analyzed, 30% had ocular hypertension (OHT) and 70% had primary open-angle glaucoma (POAG). The data was split into 56 eyes for SLT as first-line treatment and 140 eyes for SLT following prior topical therapy. The first-line SLT group was approximately five years younger and had a greater proportion of OHT patients (57% vs. 19%).  The primary outcome measurements of the study were: a reduction in IOP following drops, reduction in IOP following SLT and overall reduction. Results were reported by their correlation coefficient (denoted r, range of -1 to +1), which quantifies the strength and direction of a linear relationship between two variables. An r of -1 is a perfect negative and +1 is a perfect positive correlation. The results were as follows:In all three cases, a strong negative linear correlation was found between pretreatment IOP and the change in IOP for reduction following drops (r=-0.80), following SLT (r=-0.68) and overall reduction (r=-0.76).PGA drops augmented by beta-blockers gave a significantly greater reduction in IOP (14.35mm Hg) compared with eyes not treated with drops (6.88mm Hg), a prostaglandin alone (7.89mm Hg) and PGA drops plus a beta-blocker and a carbonic anhydrase inhibitor (CAI) (8.78mm Hg).Eyes that received no prior drop treatment achieved a significantly greater reduction in IOP (6.45mm Hg) compared with those using PGA drops alone (2.30mm Hg), a prostaglandin plus a beta-blocker (3.87mm Hg), PGA plus CAI (2.89mm Hg) and a combination of all three drugs (2.70mm Hg).No significant linear correlation was observed between the total energy used in SLT and the reduction in IOP achieved. In the UK, current guidelines from the National Institute of Clinical Excellence (NICE) recommend offering a generic prostaglandin or SLT as first-line treatment for eyes with OHT and mild/moderate POAG, with beta-blockers, CAIs or sympathomimetics to be offered as second-line treatment. Some limitations of the study are worth mentioning. “We had hoped to make comparisons with eyes treated with aqueous suppressants only prior to SLT,” wrote the authors, but they had very few eyes in that category. There was also a greater proportion of eyes with OHT in the SLT as first-line treatment group (57%) vs. the prior topical treatment group (19%), which they attribute to a change in guidance released in 2022 that included SLT as a first-line IOP-lowering option. “Some new patients were given SLT as first-line treatment at that time, whereas those who received prior topical therapy had their treatment initiated prior to the change of guidelines.” Later in their paper’s discussion, the authors note that, in practice, many patients are treated with two or more medications. “Numerous articles, meta-analyses and randomised controlled trials have shown the efficacy of monotherapy and adjunctive therapy for glaucoma,” they wrote. “In our cohort, we found a significantly greater reduction in IOP when PGA plus beta-blocker was used (10.48mm Hg) compared to when three different classes of drops were used. However, this is partially explained by the higher pretreatment IOP for this subgroup. Using the regression analysis to control for this, the expected reduction for the PGA plus beta-blocker subgroup is around 7.5mm Hg, still the largest of all subgroups.” The retrospective nature of the study means reasons for treatment choice were unknown, and information on when topical drop therapy was started was not available. “In cases where waiting for SLT would carry an unacceptable risk, drops may have been used to expedite a reduction in IOP,” wrote the authors. “Information on when topical drop therapy was started, if applicable, would have been advantageous. In this cohort, some eyes had been on the drops for many months or years before they were listed for SLT and in many cases, this will have predated the new NICE guidelines on using SLT as first-line treatment.” The authors concluded that SLT is still effective following various combinations of drops, and wrote, “However, the lack of significant additional benefit in using PGA prior to SLT compared with using SLT alone strongly supports the case for offering SLT as a first-line treatment rather than as an adjunct treatment to PGAs.”Click here for the journal source. Davies F, Butler MK. Selective laser trabeculoplasty (SLT) outcomes following topical therapy. Eye. January 12, 2026. [Epub ahead of print]. This article was developed by the editorial staff in conjunction with experts in the field. In the process, AI may have been among the editorial tools used to meet the goals of human editors, who approved all content.