Purpose: To identify the optimal energy level to be used in selective laser trabeculoplasty (SLT) for maximal intraocular pressure (IOP) reduction in open-angle glaucoma (OAG) patients.
Patients and methods: This cohort sequentially recruited OAG subjects in Hong Kong, China during 2011 to 2012. All subjects received a single session of SLT with near confluent spots to 360 degrees of the trabecular meshwork. An initial energy of 0.8 mJ was titrated until bubble formation was just visible. The main outcomes included: change in IOP (pre-SLT to 1 mo post-SLT) and total SLT energy (SLT spots multiplied by the mean energy). For statistical analysis, only the right eye of each subject was used. Bandwidth selection by generalized cross-validation was used to determine the optimal interval and point of total SLT energy that resulted in the largest IOP reduction.
Results: A total of 49 Chinese OAG subjects had a mean age of 64.2±11.1 years. The pre-SLT IOP was 17.1±2.9 mm Hg while on 1.9±1.1 types of antiglaucoma eye drops. The mean total energy was 167.1±41.4 mJ (171.5±41.2 spots at 1.0±0.06 mJ). The 1 month post-SLT IOP was 13.5±2.8 mm Hg. The percentage of SLT success was 57.1% (28/49). The 95% confidence band by bootstrap method was plotted showing that a total energy between 214.6 and 234.9 mJ significantly decreased the IOP>25%, with the optimal total energy at 226.1 mJ.
Conclusions: A higher SLT energy, in the range of 214.6 to 234.9 mJ, seems to be associated with an improved IOP-lowering response. Further randomized control trials with treatment stratification are needed to confirm these results.