Is the size of the trabecular meshwork associated with the efficacy of the selective laser trabeculoplasty?

Abstract

Purpose : Selective laser trabeculoplasty (SLT) treatment is supposed to work by modifying the metabolic activity and biomechanics of trabecular meshwork (TM). The laser spot is fixed at 400μm; this is considered large enough to cover the majority of the TM. We hypothesize that different sizes of TM might result in different percentages of tissue exposed to laser, causing a different response to treatment. We tested the hypothesis that TM dimensions measured by optical coherence tomography (OCT) affect the outcome of the SLT treatment.

Methods : A retrospective chart review of patients submitted to SLT for the treatment of open-angle glaucoma (OAG) that underwent previous OCT scans of anterior chamber angle (ACA) and with a minimum follow-up of 6 months was performed.
Success was defined as ≥ 20% of pre-treatment IOP decrease or ≥1 medication reduction without additional IOP lowering procedures at six months post-treatment. The following TM measurements were obtained: TM’s length, TM maximum thickness, TM area. Other potential predictors studied were pretreatment IOP, age, gender, glaucoma stage, type of glaucoma, and the number of IOP-lowering medications. The associations between predictors and the outcome were assessed by logistic regression analysis.

Results : Sixty-eight eyes were included in the analysis. The mean (sd) age was 73(21) years. 57 (84%) patients were affected by primary OAG, whereas 11 (16%) by pseudoexfoliative OAG. The measurements of the TM’s length, TM maximum thickness, and TM area were achieved in 75%, 80%, and 73% of cases, respectively. TM’s length, TM maximum thickness, and TM area were 734 (96) µm, 164(49) µm, and 0.089 (0.033) mm², respectively. No TM meshwork measurement predicted the successful SLT. The only significant predictor was the pretreatment IOP (OR= 1.10; p= 0.021).

Conclusions : TM measurements were not associated with the outcome. SLT effect was predicted by higher pre-treatment IOP but not by other eye features or demographic data. OCT can be helpful as a complementary exam to gonioscopy to document the open-angle before treatment but failed to have a role in the prediction of effectiveness.

This is a 2020 ARVO Annual Meeting abstract.