Intraocular Pressure Results With Trabeculectomy Ab Interno Versus Micro-Bypass Shunt
Purpose
The purpose of this study is to compare the intraocular pressure (IOP) outcomes of trabeculectomy ab interno (Trabectome) and micro-bypass shunt (iStent). The only previously published data on this topic is an abstract comparing Trabectome to the insertion of two iStent’s, although typically only one shunt is inserted.
Methods
This retrospective study enrolled patients who received either trabeculectomy ab interno with the Trabectome (Neomedix, Tustin, CA) or micro-bypass shunt with the iStent (Glaukos, Laguna Hills) at our institution. Inclusion criteria were patients with a diagnosis of open-angle glaucoma with an IOP above target after maximally tolerated medical or laser therapy. All cases except 7 trabectomes were combined with phacoemulsification. The main outcome measure was the IOP at 6 months. Statistical analysis was performed using a Student’s t-test. Kaplan-Meier survival curves were analyzed, where failure was defined as an IOP > 18 at two consecutive visits after postoperative week one.
Results
A total of 76 patients were included with a mean age of 76.3±9.2 years. In 46 patients who underwent Trabectome, the IOP was reduced from 19.4±5.8 mmHg to 15.8±3.8 (p<0.05) on 1.4 fewer medications (p<0.05) at 6 months. In 30 patients who underwent iStent, the IOP was reduced from 16±3.1 to 13.2±2.6 (p<0.05) on one less medication (p<0.05). Both groups demonstrated a mean IOP decrease of 18% (p=0.12). Kaplan-Meier survival analysis demonstrated a 6 month survival rate of 64% after Trabectome and 83% after iStent (p=0.12). There were 3 cases of cystoid macular edema only after trabectome.
Conclusion
Preliminary evidence suggests that Trabectome lead to similar IOP outcomes as compared to the insertion of a single iStent. Further study with longer follow up can also help identify risk factors that may be used to help predict which patients would benefit from surgeries with overlapping indications.