Do and colleagues report the results of a retrospective multicenter study comparing two surgical approaches for the placement of the XEN45 gel stent. The analysis includes outcomes from three academic centers, and examined change in IOP from baseline, rates of revision, and rates of treatment failure, comparing an open to a closed approach to stent placement in a group of 137 eyes. In both the open or closed procedures, an ab interno or ab externo approach was allowed. However, surgeons who utilized an open approach created a peritomy with dissection of underlying Tenons to bare sclera prior to injection of the stent, whereas in the closed approach, the stent was deployed into the subconjunctival space without prior dissection. A variable dose of mitomycin C was also injected in the subconjunctival space prior to stent insertion in both groups.
After controlling for factors such as surgeon and dose of mitomycin C utilized, the study found that percentage change in IOP from baseline was higher in the open group compared to the closed group (43.1% vs. 24.8%, respectively).
The study had several other notable findings; rates of operative revision and bleb needling, as well as rates of tube erosion and iris plugging, were significantly lower in the open group compared to the closed group.
The most significant limitation of the study is that the IOP at baseline significantly differed between the open and closed groups, with the open group having a higher pre-intervention IOP. It may be easier to achieve a higher percentage decrease in IOP compared to a lower starting IOP resulting in greater treatment efficacy. Also, eyes in the open group were significantly more likely to have undergone previous glaucoma filtration surgeries which affect the quality of the conjunctiva and Tenons, and may impact postoperative filtration success and complication rates.1 In short, the two study groups were not comparably matched across these two important features; future studies may benefit from more closely matched open versus closed groups. Another consideration is that only 55 patients were followed out to 12 months postoperatively. As subconjunctival filtration procedures often have variable outcomes in the first year after surgery, it would be of interest to follow the entire cohort for at least one year postoperatively.2,3
Do et al.'s findings suggest that XEN 45 Gel Stent placement through an open approach, while being more invasive, decreases complications and the need for post-operative bleb needling, and overall may have greater IOP- lowering efficacy.
XEN 45 Gel Stent placement through an open approach, while being more invasive, decreases complications and the need for post-operative bleb needling, and overall may have greater IOP- lowering efficacy