West Indies Glaucoma Laser Study (WIGLS)—2: Predictors of Selective Laser Trabeculoplasty Efficacy in Afro-Caribbeans With Glaucoma

Abstract

To identify factors associated with intraocular pressure (IOP) reduction following selective laser trabeculoplasty (SLT) in Afro-Caribbean people with primary open-angle glaucoma (POAG). This was a prospective stepped-wedge study. Data were drawn from 72 Afro-Caribbean subjects with POAG participating in the ongoing West Indies Glaucoma Laser Study. Multivariable mixed-model analysis was utilized to develop a predictive model for percent IOP reduction 12 months following SLT. Putative factors (age, sex, site, baseline IOP, prior use of prostaglandin therapy, number of prewashout IOP-lowering medications, central corneal thickness, severity of glaucoma, duration of follow-up, and signs of acute postoperative inflammation) were evaluated in bivariate analysis. Factors significant at P≤0.2 were included in the final model. Right and left eye data were modeled separately. At month 12 following SLT, mean IOP reductions in the West Indies Glaucoma Laser Study were 6.2 to 6.5 mm Hg (29.7% to 31.0%) in right and left eyes. The only factor significant in both eyes (P=0.0005 in right eyes and P<0.0001 in left eyes) was time, with IOP reductions being greatest at month 3 and declining slightly over time through month 12. Vertical cup-disc ratio (P=0.006) and prior prostaglandin therapy (P=0.004) were significant only in right eyes, and central corneal thickness (P=0.014) was significant only in left eyes. Factors significant only unilaterally did not approach significance in fellow eyes, suggesting the possibility that these represent type 1 errors. Site (St. Lucia vs. Dominica) was not a significant factor, establishing generalizability of these treatment outcomes to a broader population of African-derived people. This analysis did not identify any subject-specific factors consistently predictive of therapeutic response to SLT. Of note, no factors predicted a suboptimal response. These findings favorably position SLT for broad application as primary therapy in African-derived people with POAG.