Immune system could play role in IOP reduction after SLT, study finds
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Key takeaways:
- Selective laser trabeculoplasty yielded less IOP reduction over time in immunosuppressed patients, but the treatment remained effective.
- The immune system could be involved in regulating IOP after SLT.
Patients on systemic immunosuppressive therapy experienced diminished IOP reductions a year after receiving selective laser trabeculoplasty compared with those who were not immunosuppressed, according to a study.
The results suggest that the immune system could be involved in IOP regulation after SLT, Mayo Clinic researchers wrote in the Journal of Glaucoma. The retrospective study analyzed 4 years of Mayo Clinic charts to shine light on SLT’s mechanism of action and its efficacy in an immunosuppressed population.
Researchers analyzed a group of patients who underwent SLT at Mayo Clinic while actively receiving at least one systemic immunosuppressive medication (n = 72 patients; 108 treated eyes) and compared them over 12 months with a control group not receiving immunosuppressive agents (n = 1,417 patients; 1,997 treated eyes).
After researchers adjusted for age, the immunosuppressive and control groups had no significant difference in percentage of IOP reduction (mean, –16% vs. –18.8%, P = .26) at 1 to 2 months after the procedure. A nonsignificant trend toward greater IOP reduction emerged in the control group (mean, –18.3% vs. –15.2%, P = .062) between 3 to 6 months. And at 12 months after SLT, the control group’s mean IOP reduction advanced to –20.3%, while the immunosuppressive group’s decreased to –15.1% (P = .045).
The difference in IOP reduction at 12 months remained after researchers adjusted for potential confounding variables, including attrition and systemic steroid use.
Patients in both groups had similar glaucoma subtypes and history of prior glaucoma intervention and had no difference in baseline IOP before intervention in the study. The control group was significantly older than the immunosuppressed group (mean age, 74 years vs. 70.7 years; P < .001), but the groups had a similar sex distribution (53.5% women vs. 63% women; P = .12).
Patients taking immunosuppressive medication were most commonly being treated for underlying autoimmune or inflammatory disease, particularly rheumatoid arthritis.
One of the study’s limitations was that the control group was much larger than the immunosuppressive group. Also, there was no standardization of when to offer SLT, or whether perioperative topical NSAIDs or corticosteroids were given afterwards, researchers wrote.
The study concluded that the benefits of SLT may diminish over time for patients on immunosuppressive therapy, but the procedure remains an effective treatment option for IOP reduction in that population. The results could support a cellular theory of SLT’s mechanism of action, researchers wrote, calling for future studies to identify the specific pathways involved.
Perspective
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SLT’s exact mechanism of action has been thoroughly debated since its entry into the glaucoma treatment universe. The fact is indisputable that with SLT there is minimal mechanical alteration of the trabecular architecture; therefore, it’s sensible that the biological modification that results in lowering of IOP is at minimum mitigated by some form of a local/ocular immune response that enhances outflow.
Whether a broader systemic immune activation plays a significant role in SLT’s efficacy was the hypothesis cleverly posed by the authors, which they attempted to answer by involving a cohort of immunosuppressed glaucoma patients eligible for SLT.
The authors noted that although no immune-mediated pathway was confirmed with this study, the diminished IOP-lowering effectiveness at 12 months in the immunosuppressed group, coupled with the increased IOP-lowering effectiveness in the control group, does suggest that the broader immune system may be involved in SLT’s biological effects on outflow.
This was an insightful study that used careful methodology and analysis, and undoubtedly contributes to the greater body of understanding on SLT. Although no confirmatory mechanistic evidence came out of this study, its results are valuable for our patients who have glaucoma and require systemic immunosuppression.
Although more studies are needed on this subset of patients at present, we should consider tempering our expectations of SLT’s effectiveness in this group and adapt our treatment and management accordingly.
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