SLT Efficacy Affected by Baseline IOP, Surgeon Skill, Corneal Thickness and Others

The paradigm of glaucoma management has shifted in recent years as evidence has increasingly supported forgoing topical drops as first-line therapy, instead opting for selective laser trabeculoplasty (SLT). In a retrospective review of data from the Swedish Optimal SLT (OSLT) trial, researchers analyzed the impact of specific variables on efficacy of the procedure. The 360/high strategy resulted in the most ocular hyperemia, pain and photophobia, which are symptoms commonly experienced during anterior intraocular inflammation. This graph from the study shows a scatterplot of baseline IOP and IOP reduction one to six months after SLT. Photo: Dahlgren T, et al. Ophthalmol Sci. September 2, 2025. Click image to enlarge. The paper, appearing in Ophthalmology Glaucoma, included 512 eyes from 399 patients enrolled in the OSLT trial, who were randomized to one of four SLT variants: 180° or 360° and standard or high laser power. Outcomes were primarily determined by intraocular pressure (IOP) reduction one to six months following the operation. After analysis, the researchers determined that the 360/high protocol remained the most effective of the SLT variants. Both absolute and relative IOP reduction had a positive predictor of higher baseline IOP, and a greater pressure reduction from prior SLT, as well as IOP lowering in the contralateral eye, were also highly positive predictors. Conversely, decreased SLT efficacy was associated with pseudoexfoliation, number of prior SLT procedures and increased corneal thickness. While consultants/specialists and residents achieved similar results, individual performance by the surgeon mattered, and dominant hand usage was part of this. Interestingly, efficacy did not seem to be affected by factors of age, glaucoma medication, cataract surgery, anterior chamber angle pigmentation, inflammatory symptoms or postoperative anterior chamber flare.The authors of the study warn that interpreting repeat SLT results must come with caution, since those with large and long-lasting effects from prior SLT are likely not as well-represented as those with less long-lasting responses, thus more frequent occurrence of SLT. However, for a patient not responding to previous SLT, the surgeon may opt for alternative treatments, leading to underrepresentation.  The investigators believe that, “taken together, we conclude that SLT repetition is clearly advisable if a prior SLT (in either eye) was successful, could still be tried if it was not, and that we look forward to future trials that may shed more light on multiple-repeat SLT efficacy.”While pseudoexfoliation was a negative predictor for SLT efficacy, the authors relay that this still should not discourage use of the strategy in these eyes, as significant IOP reduction still occurred—especially with 360/high SLT—achieving a mean IOPR of 20%. As for the negative predictor of increased corneal thickness, the researchers believe this may be due to greater corneal rigidity giving falsely high tonometry measurements, in turn overestimating true IOP, making the potentiating effect of baseline IOP on SLT efficacy lower than expected in thicker cornea eyes.Clinically, the authors suggest that “the 360 protocol was not only more efficacious than the alternatives but also more robust and less vulnerable to impact from negative predictors.”Click here for the journal source. Dahlgren T, Ayala M, Zetterberg M. Predictors of selective laser trabeculoplasty efficacy results from the Swedish Optimal SLT Multicenter Randomized Controlled Trial. Ophthalmol Sci. September 2, 2025. [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.