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Selective laser trabeculoplasty (SLT) is often performed as an adjunct therapy in patients already on medications. In this study, the authors examined the effect of SLT in patients on maximally tolerated therapy. The paper answers a relevant question regarding predictors of SLT efficacy in patients already on multiple medications (mean 2.9 ± 0.9). The cohort included patients with normal pressure glaucoma (NPG, 27% of subjects). Patients with NPG pose a particular challenge as treatment aims to lower an already 'normal' intraocular pressure (IOP).
It was encouraging that SLT worked even in eyes of maximally treated patients
We know from clinical trials that a higher pre-treatment IOP tends to predict a more robust therapeutic response. So, does this concept apply to SLT in patients already on maximal therapy? Pillunat and colleagues answered this question by prospectively enrolling subjects and measuring diurnal IOP (six times/24hr) before and about six months after a single surgeon performed 360 degree SLT. The only predictor of response was pre-SLT IOP. In fact, the response to SLT was better with higher baseline IOPs (for each mmHg higher mean diurnal pre-SLT, IOP was reduced by 0.3 mmHg). This is not unexpected and is in line with findings from EMGT. IOP reduction was observed in 100% of patients with pre-SLT IOP > 18 mmHg. While patients with pre-SLT IOP < 14 mmHg had less effective results, still 64% experienced some IOP reduction (of note, in this group a third of patients had a slight increase in IOP).
The results of this study are in agreement with the literature - a higher baseline IOP tends to predict a better response. It was encouraging that SLT worked even in eyes of maximally treated patients. Perhaps the most promising finding was that SLT lowered IOP similarly in high- and normal-pressure glaucoma eyes (p = 0.887) as long as pre-SLT IOP was comparable.